diff --git a/.rustlings-state.txt b/.rustlings-state.txt
index e3eec2a..f80a4ed 100644
--- a/.rustlings-state.txt
+++ b/.rustlings-state.txt
@@ -1,6 +1,6 @@
 DON'T EDIT THIS FILE!
 
-structs1
+as_ref_mut
 
 intro1
 intro2
@@ -31,4 +31,68 @@ move_semantics1
 move_semantics2
 move_semantics3
 move_semantics4
-move_semantics5
\ No newline at end of file
+move_semantics5
+structs1
+structs2
+structs3
+enums1
+enums2
+enums3
+strings1
+strings2
+strings3
+strings4
+modules1
+modules2
+modules3
+hashmaps1
+hashmaps2
+hashmaps3
+quiz2
+options1
+options2
+options3
+errors1
+errors2
+errors3
+errors4
+errors5
+errors6
+generics1
+generics2
+traits1
+traits2
+traits3
+traits4
+traits5
+quiz3
+lifetimes1
+lifetimes2
+lifetimes3
+tests1
+tests2
+tests3
+iterators1
+iterators2
+iterators3
+iterators4
+iterators5
+box1
+rc1
+arc1
+cow1
+threads1
+threads2
+threads3
+macros1
+macros2
+macros3
+macros4
+clippy1
+clippy2
+clippy3
+using_as
+from_into
+from_str
+try_from_into
+as_ref_mut
\ No newline at end of file
diff --git a/exercises/07_structs/structs1.rs b/exercises/07_structs/structs1.rs
index 959c4c6..e84a90d 100644
--- a/exercises/07_structs/structs1.rs
+++ b/exercises/07_structs/structs1.rs
@@ -1,12 +1,15 @@
 struct ColorRegularStruct {
     // TODO: Add the fields that the test `regular_structs` expects.
     // What types should the fields have? What are the minimum and maximum values for RGB colors?
+    red: u8,
+    green: u8,
+    blue: u8,
 }
 
-struct ColorTupleStruct(/* TODO: Add the fields that the test `tuple_structs` expects */);
+struct ColorTupleStruct(u8, u8, u8);
 
 #[derive(Debug)]
-struct UnitStruct;
+struct UnitStruct();
 
 fn main() {
     // You can optionally experiment here.
@@ -19,7 +22,11 @@ mod tests {
     #[test]
     fn regular_structs() {
         // TODO: Instantiate a regular struct.
-        // let green =
+        let green = ColorRegularStruct {
+            red: 0,
+            green: 255,
+            blue: 0,
+        };
 
         assert_eq!(green.red, 0);
         assert_eq!(green.green, 255);
@@ -29,7 +36,7 @@ mod tests {
     #[test]
     fn tuple_structs() {
         // TODO: Instantiate a tuple struct.
-        // let green =
+        let green = ColorTupleStruct(0, 255, 0);
 
         assert_eq!(green.0, 0);
         assert_eq!(green.1, 255);
@@ -39,7 +46,7 @@ mod tests {
     #[test]
     fn unit_structs() {
         // TODO: Instantiate a unit struct.
-        // let unit_struct =
+        let unit_struct = UnitStruct();
         let message = format!("{unit_struct:?}s are fun!");
 
         assert_eq!(message, "UnitStructs are fun!");
diff --git a/exercises/07_structs/structs2.rs b/exercises/07_structs/structs2.rs
index 79141af..d5c18cb 100644
--- a/exercises/07_structs/structs2.rs
+++ b/exercises/07_structs/structs2.rs
@@ -34,7 +34,11 @@ mod tests {
         let order_template = create_order_template();
 
         // TODO: Create your own order using the update syntax and template above!
-        // let your_order =
+        let your_order = Order {
+            name: "Hacker in Rust".to_string(),
+            count: 1,
+            ..order_template
+        };
 
         assert_eq!(your_order.name, "Hacker in Rust");
         assert_eq!(your_order.year, order_template.year);
diff --git a/exercises/07_structs/structs3.rs b/exercises/07_structs/structs3.rs
index 69e5ced..2526a1a 100644
--- a/exercises/07_structs/structs3.rs
+++ b/exercises/07_structs/structs3.rs
@@ -24,14 +24,16 @@ impl Package {
     }
 
     // TODO: Add the correct return type to the function signature.
-    fn is_international(&self) {
+    fn is_international(&self) -> bool {
         // TODO: Read the tests that use this method to find out when a package
         // is considered international.
+        self.sender_country != self.recipient_country
     }
 
     // TODO: Add the correct return type to the function signature.
-    fn get_fees(&self, cents_per_gram: u32) {
+    fn get_fees(&self, cents_per_gram: u32) -> u32 {
         // TODO: Calculate the package's fees.
+        cents_per_gram * self.weight_in_grams
     }
 }
 
diff --git a/exercises/08_enums/enums1.rs b/exercises/08_enums/enums1.rs
index c0d0c30..c45ac7a 100644
--- a/exercises/08_enums/enums1.rs
+++ b/exercises/08_enums/enums1.rs
@@ -1,6 +1,11 @@
 #[derive(Debug)]
 enum Message {
     // TODO: Define a few types of messages as used below.
+    Resize,
+    Move,
+    Echo,
+    ChangeColor,
+    Quit,
 }
 
 fn main() {
diff --git a/exercises/08_enums/enums2.rs b/exercises/08_enums/enums2.rs
index d70f639..ead7002 100644
--- a/exercises/08_enums/enums2.rs
+++ b/exercises/08_enums/enums2.rs
@@ -7,6 +7,11 @@ struct Point {
 #[derive(Debug)]
 enum Message {
     // TODO: Define the different variants used below.
+    Resize { width: usize, height: usize },
+    Move(Point),
+    Echo(String),
+    ChangeColor(u8, u8, u8),
+    Quit,
 }
 
 impl Message {
diff --git a/exercises/08_enums/enums3.rs b/exercises/08_enums/enums3.rs
index cb05f65..1282c40 100644
--- a/exercises/08_enums/enums3.rs
+++ b/exercises/08_enums/enums3.rs
@@ -46,6 +46,13 @@ impl State {
     fn process(&mut self, message: Message) {
         // TODO: Create a match expression to process the different message
         // variants using the methods defined above.
+        match message {
+            Message::Resize { width, height } => self.resize(width, height),
+            Message::Move(point) => self.move_position(point),
+            Message::Echo(string) => self.echo(string),
+            Message::ChangeColor(red, green, blue) => self.change_color(red, green, blue),
+            Message::Quit => self.quit(),
+        }
     }
 }
 
diff --git a/exercises/09_strings/strings1.rs b/exercises/09_strings/strings1.rs
index 6abdbb4..eb70e50 100644
--- a/exercises/09_strings/strings1.rs
+++ b/exercises/09_strings/strings1.rs
@@ -1,5 +1,5 @@
 // TODO: Fix the compiler error without changing the function signature.
-fn current_favorite_color() -> String {
+fn current_favorite_color() -> &'static str {
     "blue"
 }
 
diff --git a/exercises/09_strings/strings2.rs b/exercises/09_strings/strings2.rs
index 93d9cb6..2ed89c5 100644
--- a/exercises/09_strings/strings2.rs
+++ b/exercises/09_strings/strings2.rs
@@ -6,7 +6,7 @@ fn is_a_color_word(attempt: &str) -> bool {
 fn main() {
     let word = String::from("green"); // Don't change this line.
 
-    if is_a_color_word(word) {
+    if is_a_color_word(&word) {
         println!("That is a color word I know!");
     } else {
         println!("That is not a color word I know.");
diff --git a/exercises/09_strings/strings3.rs b/exercises/09_strings/strings3.rs
index f5e45b0..b7d77f5 100644
--- a/exercises/09_strings/strings3.rs
+++ b/exercises/09_strings/strings3.rs
@@ -1,13 +1,16 @@
 fn trim_me(input: &str) -> &str {
     // TODO: Remove whitespace from both ends of a string.
+    input.trim_ascii()
 }
 
 fn compose_me(input: &str) -> String {
     // TODO: Add " world!" to the string! There are multiple ways to do this.
+    input.to_owned() + " world!"
 }
 
 fn replace_me(input: &str) -> String {
     // TODO: Replace "cars" in the string with "balloons".
+    input.to_owned().replace("cars", "balloons")
 }
 
 fn main() {
diff --git a/exercises/09_strings/strings4.rs b/exercises/09_strings/strings4.rs
index 4730726..c0b875b 100644
--- a/exercises/09_strings/strings4.rs
+++ b/exercises/09_strings/strings4.rs
@@ -1,6 +1,3 @@
-// Calls of this function should be replaced with calls of `string_slice` or `string`.
-fn placeholder() {}
-
 fn string_slice(arg: &str) {
     println!("{arg}");
 }
@@ -13,25 +10,25 @@ fn string(arg: String) {
 // Your task is to replace `placeholder(…)` with either `string_slice(…)`
 // or `string(…)` depending on what you think each value is.
 fn main() {
-    placeholder("blue");
+    string_slice("blue"); // &str
 
-    placeholder("red".to_string());
+    string("red".to_string()); // String
 
-    placeholder(String::from("hi"));
+    string(String::from("hi")); // String
 
-    placeholder("rust is fun!".to_owned());
+    string("rust is fun!".to_owned()); // String
 
-    placeholder("nice weather".into());
+    string("nice weather".into()); // String
 
-    placeholder(format!("Interpolation {}", "Station"));
+    string(format!("Interpolation {}", "Station")); // String
 
     // WARNING: This is byte indexing, not character indexing.
     // Character indexing can be done using `s.chars().nth(INDEX)`.
-    placeholder(&String::from("abc")[0..1]);
+    string_slice(&String::from("abc")[0..1]); // &str
 
-    placeholder("  hello there ".trim());
+    string_slice("  hello there ".trim()); // &str
 
-    placeholder("Happy Monday!".replace("Mon", "Tues"));
+    string("Happy Monday!".replace("Mon", "Tues")); // String
 
-    placeholder("mY sHiFt KeY iS sTiCkY".to_lowercase());
+    string("mY sHiFt KeY iS sTiCkY".to_lowercase()); // String
 }
diff --git a/exercises/10_modules/modules1.rs b/exercises/10_modules/modules1.rs
index d97ab23..81981df 100644
--- a/exercises/10_modules/modules1.rs
+++ b/exercises/10_modules/modules1.rs
@@ -5,7 +5,7 @@ mod sausage_factory {
         String::from("Ginger")
     }
 
-    fn make_sausage() {
+    pub fn make_sausage() {
         get_secret_recipe();
         println!("sausage!");
     }
diff --git a/exercises/10_modules/modules2.rs b/exercises/10_modules/modules2.rs
index 782a70e..3cabbfd 100644
--- a/exercises/10_modules/modules2.rs
+++ b/exercises/10_modules/modules2.rs
@@ -3,8 +3,8 @@
 
 mod delicious_snacks {
     // TODO: Add the following two `use` statements after fixing them.
-    // use self::fruits::PEAR as ???;
-    // use self::veggies::CUCUMBER as ???;
+    pub use self::fruits::PEAR as fruit;
+    pub use self::veggies::CUCUMBER as veggie;
 
     mod fruits {
         pub const PEAR: &str = "Pear";
diff --git a/exercises/10_modules/modules3.rs b/exercises/10_modules/modules3.rs
index 691608d..403b7ea 100644
--- a/exercises/10_modules/modules3.rs
+++ b/exercises/10_modules/modules3.rs
@@ -3,7 +3,7 @@
 
 // TODO: Bring `SystemTime` and `UNIX_EPOCH` from the `std::time` module into
 // your scope. Bonus style points if you can do it with one line!
-// use ???;
+use std::time::{SystemTime, UNIX_EPOCH};
 
 fn main() {
     match SystemTime::now().duration_since(UNIX_EPOCH) {
diff --git a/exercises/11_hashmaps/hashmaps1.rs b/exercises/11_hashmaps/hashmaps1.rs
index 74001d0..625d023 100644
--- a/exercises/11_hashmaps/hashmaps1.rs
+++ b/exercises/11_hashmaps/hashmaps1.rs
@@ -8,10 +8,12 @@ use std::collections::HashMap;
 
 fn fruit_basket() -> HashMap<String, u32> {
     // TODO: Declare the hash map.
-    // let mut basket =
+    let mut basket = HashMap::<String, u32>::new();
 
     // Two bananas are already given for you :)
     basket.insert(String::from("banana"), 2);
+    basket.insert(String::from("apple"), 2);
+    basket.insert(String::from("mango"), 2);
 
     // TODO: Put more fruits in your basket.
 
diff --git a/exercises/11_hashmaps/hashmaps2.rs b/exercises/11_hashmaps/hashmaps2.rs
index e9f53fe..c71525f 100644
--- a/exercises/11_hashmaps/hashmaps2.rs
+++ b/exercises/11_hashmaps/hashmaps2.rs
@@ -32,6 +32,7 @@ fn fruit_basket(basket: &mut HashMap<Fruit, u32>) {
         // TODO: Insert new fruits if they are not already present in the
         // basket. Note that you are not allowed to put any type of fruit that's
         // already present!
+        basket.entry(fruit).or_insert(1);
     }
 }
 
diff --git a/exercises/11_hashmaps/hashmaps3.rs b/exercises/11_hashmaps/hashmaps3.rs
index 5b390ab..7d517b8 100644
--- a/exercises/11_hashmaps/hashmaps3.rs
+++ b/exercises/11_hashmaps/hashmaps3.rs
@@ -31,13 +31,47 @@ fn build_scores_table(results: &str) -> HashMap<&str, TeamScores> {
         // Keep in mind that goals scored by team 1 will be the number of goals
         // conceded by team 2. Similarly, goals scored by team 2 will be the
         // number of goals conceded by team 1.
-    }
+        scores
+            .entry(team_1_name)
+            .and_modify(|current_team_1_scores| {
+                current_team_1_scores.goals_scored += team_1_score;
+                current_team_1_scores.goals_conceded += team_2_score
+            })
+            .or_insert(TeamScores {
+                goals_scored: team_1_score,
+                goals_conceded: team_2_score,
+            });
 
+        scores
+            .entry(team_2_name)
+            .and_modify(|current_team_2_scores| {
+                current_team_2_scores.goals_scored += team_2_score;
+                current_team_2_scores.goals_conceded += team_1_score
+            })
+            .or_insert(TeamScores {
+                goals_scored: team_2_score,
+                goals_conceded: team_1_score,
+            });
+    }
     scores
 }
 
 fn main() {
     // You can optionally experiment here.
+    const RESULTS: &str = "England,France,4,2
+France,Italy,3,1
+Poland,Spain,2,0
+Germany,England,2,1
+England,Spain,1,0";
+
+    let scores = build_scores_table(RESULTS);
+
+    for (key, value) in &scores {
+        println!(
+            "{key}: (scored: {0}, conceeded: {1})",
+            value.goals_scored, value.goals_conceded
+        );
+    }
 }
 
 #[cfg(test)]
@@ -54,9 +88,11 @@ England,Spain,1,0";
     fn build_scores() {
         let scores = build_scores_table(RESULTS);
 
-        assert!(["England", "France", "Germany", "Italy", "Poland", "Spain"]
-            .into_iter()
-            .all(|team_name| scores.contains_key(team_name)));
+        assert!(
+            ["England", "France", "Germany", "Italy", "Poland", "Spain"]
+                .into_iter()
+                .all(|team_name| scores.contains_key(team_name))
+        );
     }
 
     #[test]
diff --git a/exercises/12_options/options1.rs b/exercises/12_options/options1.rs
index d0c412a..9f0bef9 100644
--- a/exercises/12_options/options1.rs
+++ b/exercises/12_options/options1.rs
@@ -4,6 +4,11 @@
 // `hour_of_day` is higher than 23.
 fn maybe_ice_cream(hour_of_day: u16) -> Option<u16> {
     // TODO: Complete the function body.
+    match hour_of_day {
+        0..22 => Some(5),
+        22..=23 => Some(0),
+        _ => None,
+    }
 }
 
 fn main() {
@@ -18,7 +23,7 @@ mod tests {
     fn raw_value() {
         // TODO: Fix this test. How do you get the value contained in the
         // Option?
-        let ice_creams = maybe_ice_cream(12);
+        let ice_creams = maybe_ice_cream(12).unwrap();
 
         assert_eq!(ice_creams, 5); // Don't change this line.
     }
diff --git a/exercises/12_options/options2.rs b/exercises/12_options/options2.rs
index 07c27c6..1039d61 100644
--- a/exercises/12_options/options2.rs
+++ b/exercises/12_options/options2.rs
@@ -10,7 +10,7 @@ mod tests {
         let optional_target = Some(target);
 
         // TODO: Make this an if-let statement whose value is `Some`.
-        word = optional_target {
+        if let Some(word) = optional_target {
             assert_eq!(word, target);
         }
     }
@@ -29,7 +29,7 @@ mod tests {
         // TODO: Make this a while-let statement. Remember that `Vec::pop()`
         // adds another layer of `Option`. You can do nested pattern matching
         // in if-let and while-let statements.
-        integer = optional_integers.pop() {
+        while let Some(Some(integer)) = optional_integers.pop() {
             assert_eq!(integer, cursor);
             cursor -= 1;
         }
diff --git a/exercises/12_options/options3.rs b/exercises/12_options/options3.rs
index c97b1d3..aecb7a5 100644
--- a/exercises/12_options/options3.rs
+++ b/exercises/12_options/options3.rs
@@ -9,7 +9,7 @@ fn main() {
 
     // TODO: Fix the compiler error by adding something to this match statement.
     match optional_point {
-        Some(p) => println!("Coordinates are {},{}", p.x, p.y),
+        Some(ref p) => println!("Coordinates are {},{}", p.x, p.y),
         _ => panic!("No match!"),
     }
 
diff --git a/exercises/13_error_handling/errors1.rs b/exercises/13_error_handling/errors1.rs
index e07fddc..fcc4aea 100644
--- a/exercises/13_error_handling/errors1.rs
+++ b/exercises/13_error_handling/errors1.rs
@@ -4,12 +4,12 @@
 // construct to `Option` that can be used to express error conditions. Change
 // the function signature and body to return `Result<String, String>` instead
 // of `Option<String>`.
-fn generate_nametag_text(name: String) -> Option<String> {
+fn generate_nametag_text(name: String) -> Result<String, String> {
     if name.is_empty() {
         // Empty names aren't allowed
-        None
+        Err("Empty names aren't allowed".into())
     } else {
-        Some(format!("Hi! My name is {name}"))
+        Ok(format!("Hi! My name is {name}"))
     }
 }
 
diff --git a/exercises/13_error_handling/errors2.rs b/exercises/13_error_handling/errors2.rs
index defe359..3d850f7 100644
--- a/exercises/13_error_handling/errors2.rs
+++ b/exercises/13_error_handling/errors2.rs
@@ -21,7 +21,7 @@ fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {
     let cost_per_item = 5;
 
     // TODO: Handle the error case as described above.
-    let qty = item_quantity.parse::<i32>();
+    let qty = item_quantity.parse::<i32>()?;
 
     Ok(qty * cost_per_item + processing_fee)
 }
diff --git a/exercises/13_error_handling/errors3.rs b/exercises/13_error_handling/errors3.rs
index 8e8c38a..84ac530 100644
--- a/exercises/13_error_handling/errors3.rs
+++ b/exercises/13_error_handling/errors3.rs
@@ -15,7 +15,7 @@ fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {
 
 // TODO: Fix the compiler error by changing the signature and body of the
 // `main` function.
-fn main() {
+fn main() -> Result<(), ParseIntError> {
     let mut tokens = 100;
     let pretend_user_input = "8";
 
@@ -24,8 +24,10 @@ fn main() {
 
     if cost > tokens {
         println!("You can't afford that many!");
+        Ok(())
     } else {
         tokens -= cost;
         println!("You now have {tokens} tokens.");
+        Ok(())
     }
 }
diff --git a/exercises/13_error_handling/errors4.rs b/exercises/13_error_handling/errors4.rs
index 144fce7..cda83ca 100644
--- a/exercises/13_error_handling/errors4.rs
+++ b/exercises/13_error_handling/errors4.rs
@@ -11,7 +11,11 @@ impl PositiveNonzeroInteger {
     fn new(value: i64) -> Result<Self, CreationError> {
         // TODO: This function shouldn't always return an `Ok`.
         // Read the tests below to clarify what should be returned.
-        Ok(Self(value as u64))
+        match value {
+            x if x < 0 => Err(CreationError::Negative),
+            0 => Err(CreationError::Zero),
+            x => Ok(PositiveNonzeroInteger(x as u64)),
+        }
     }
 }
 
diff --git a/exercises/13_error_handling/errors5.rs b/exercises/13_error_handling/errors5.rs
index 125779b..405f0dc 100644
--- a/exercises/13_error_handling/errors5.rs
+++ b/exercises/13_error_handling/errors5.rs
@@ -48,7 +48,7 @@ impl PositiveNonzeroInteger {
 
 // TODO: Add the correct return type `Result<(), Box<dyn ???>>`. What can we
 // use to describe both errors? Is there a trait which both errors implement?
-fn main() {
+fn main() -> Result<(), Box<dyn Error>> {
     let pretend_user_input = "42";
     let x: i64 = pretend_user_input.parse()?;
     println!("output={:?}", PositiveNonzeroInteger::new(x)?);
diff --git a/exercises/13_error_handling/errors6.rs b/exercises/13_error_handling/errors6.rs
index b1995e0..353b50b 100644
--- a/exercises/13_error_handling/errors6.rs
+++ b/exercises/13_error_handling/errors6.rs
@@ -25,7 +25,9 @@ impl ParsePosNonzeroError {
     }
 
     // TODO: Add another error conversion function here.
-    // fn from_parse_int(???) -> Self { ??? }
+    fn from_parse_int(err: ParseIntError) -> Self {
+        Self::ParseInt(err)
+    }
 }
 
 #[derive(PartialEq, Debug)]
@@ -43,7 +45,7 @@ impl PositiveNonzeroInteger {
     fn parse(s: &str) -> Result<Self, ParsePosNonzeroError> {
         // TODO: change this to return an appropriate error instead of panicking
         // when `parse()` returns an error.
-        let x: i64 = s.parse().unwrap();
+        let x: i64 = s.parse().map_err(ParsePosNonzeroError::from_parse_int)?;
         Self::new(x).map_err(ParsePosNonzeroError::from_creation)
     }
 }
diff --git a/exercises/14_generics/generics1.rs b/exercises/14_generics/generics1.rs
index 87ed990..7e5571f 100644
--- a/exercises/14_generics/generics1.rs
+++ b/exercises/14_generics/generics1.rs
@@ -6,7 +6,7 @@ fn main() {
     // TODO: Fix the compiler error by annotating the type of the vector
     // `Vec<T>`. Choose `T` as some integer type that can be created from
     // `u8` and `i8`.
-    let mut numbers = Vec::new();
+    let mut numbers: Vec<i32> = Vec::new();
 
     // Don't change the lines below.
     let n1: u8 = 42;
diff --git a/exercises/14_generics/generics2.rs b/exercises/14_generics/generics2.rs
index 8908725..ba77625 100644
--- a/exercises/14_generics/generics2.rs
+++ b/exercises/14_generics/generics2.rs
@@ -1,12 +1,12 @@
 // This powerful wrapper provides the ability to store a positive integer value.
 // TODO: Rewrite it using a generic so that it supports wrapping ANY type.
-struct Wrapper {
-    value: u32,
+struct Wrapper<T> {
+    value: T,
 }
 
 // TODO: Adapt the struct's implementation to be generic over the wrapped value.
-impl Wrapper {
-    fn new(value: u32) -> Self {
+impl<T> Wrapper<T> {
+    fn new(value: T) -> Self {
         Wrapper { value }
     }
 }
diff --git a/exercises/15_traits/traits1.rs b/exercises/15_traits/traits1.rs
index 85be17e..98eb38a 100644
--- a/exercises/15_traits/traits1.rs
+++ b/exercises/15_traits/traits1.rs
@@ -6,6 +6,9 @@ trait AppendBar {
 
 impl AppendBar for String {
     // TODO: Implement `AppendBar` for the type `String`.
+    fn append_bar(self) -> String {
+        self + "Bar"
+    }
 }
 
 fn main() {
diff --git a/exercises/15_traits/traits2.rs b/exercises/15_traits/traits2.rs
index d724dc2..1a93860 100644
--- a/exercises/15_traits/traits2.rs
+++ b/exercises/15_traits/traits2.rs
@@ -4,6 +4,12 @@ trait AppendBar {
 
 // TODO: Implement the trait `AppendBar` for a vector of strings.
 // `append_bar` should push the string "Bar" into the vector.
+impl AppendBar for Vec<String> {
+    fn append_bar(mut self) -> Self {
+        self.push("Bar".into());
+        self
+    }
+}
 
 fn main() {
     // You can optionally experiment here.
diff --git a/exercises/15_traits/traits3.rs b/exercises/15_traits/traits3.rs
index c244650..0b800e7 100644
--- a/exercises/15_traits/traits3.rs
+++ b/exercises/15_traits/traits3.rs
@@ -3,7 +3,9 @@ trait Licensed {
     // implementors like the two structs below can share that default behavior
     // without repeating the function.
     // The default license information should be the string "Default license".
-    fn licensing_info(&self) -> String;
+    fn licensing_info(&self) -> String {
+        "Default license".into()
+    }
 }
 
 struct SomeSoftware {
@@ -28,10 +30,13 @@ mod tests {
     #[test]
     fn is_licensing_info_the_same() {
         let licensing_info = "Default license";
+
         let some_software = SomeSoftware { version_number: 1 };
+
         let other_software = OtherSoftware {
             version_number: "v2.0.0".to_string(),
         };
+
         assert_eq!(some_software.licensing_info(), licensing_info);
         assert_eq!(other_software.licensing_info(), licensing_info);
     }
diff --git a/exercises/15_traits/traits4.rs b/exercises/15_traits/traits4.rs
index 80092a6..b23dcdd 100644
--- a/exercises/15_traits/traits4.rs
+++ b/exercises/15_traits/traits4.rs
@@ -11,7 +11,7 @@ impl Licensed for SomeSoftware {}
 impl Licensed for OtherSoftware {}
 
 // TODO: Fix the compiler error by only changing the signature of this function.
-fn compare_license_types(software1: ???, software2: ???) -> bool {
+fn compare_license_types(software1: impl Licensed, software2: impl Licensed) -> bool {
     software1.licensing_info() == software2.licensing_info()
 }
 
diff --git a/exercises/15_traits/traits5.rs b/exercises/15_traits/traits5.rs
index 5b356ac..3f48437 100644
--- a/exercises/15_traits/traits5.rs
+++ b/exercises/15_traits/traits5.rs
@@ -19,7 +19,7 @@ impl SomeTrait for OtherStruct {}
 impl OtherTrait for OtherStruct {}
 
 // TODO: Fix the compiler error by only changing the signature of this function.
-fn some_func(item: ???) -> bool {
+fn some_func(item: impl SomeTrait + OtherTrait) -> bool {
     item.some_function() && item.other_function()
 }
 
diff --git a/exercises/16_lifetimes/lifetimes1.rs b/exercises/16_lifetimes/lifetimes1.rs
index 19e2d39..3559cae 100644
--- a/exercises/16_lifetimes/lifetimes1.rs
+++ b/exercises/16_lifetimes/lifetimes1.rs
@@ -4,12 +4,8 @@
 // not own their own data. What if their owner goes out of scope?
 
 // TODO: Fix the compiler error by updating the function signature.
-fn longest(x: &str, y: &str) -> &str {
-    if x.len() > y.len() {
-        x
-    } else {
-        y
-    }
+fn longest<'a>(x: &'a str, y: &'a str) -> &'a str {
+    if x.len() > y.len() { x } else { y }
 }
 
 fn main() {
diff --git a/exercises/16_lifetimes/lifetimes2.rs b/exercises/16_lifetimes/lifetimes2.rs
index de5a5df..b33a7c8 100644
--- a/exercises/16_lifetimes/lifetimes2.rs
+++ b/exercises/16_lifetimes/lifetimes2.rs
@@ -1,19 +1,15 @@
 // Don't change this function.
 fn longest<'a>(x: &'a str, y: &'a str) -> &'a str {
-    if x.len() > y.len() {
-        x
-    } else {
-        y
-    }
+    if x.len() > y.len() { x } else { y }
 }
 
 fn main() {
     // TODO: Fix the compiler error by moving one line.
 
     let string1 = String::from("long string is long");
+    let string2 = String::from("xyz");
     let result;
     {
-        let string2 = String::from("xyz");
         result = longest(&string1, &string2);
     }
     println!("The longest string is '{result}'");
diff --git a/exercises/16_lifetimes/lifetimes3.rs b/exercises/16_lifetimes/lifetimes3.rs
index 1cc2759..91e3922 100644
--- a/exercises/16_lifetimes/lifetimes3.rs
+++ b/exercises/16_lifetimes/lifetimes3.rs
@@ -1,9 +1,9 @@
 // Lifetimes are also needed when structs hold references.
 
 // TODO: Fix the compiler errors about the struct.
-struct Book {
-    author: &str,
-    title: &str,
+struct Book<'a> {
+    author: &'a str,
+    title: &'a str,
 }
 
 fn main() {
diff --git a/exercises/17_tests/tests1.rs b/exercises/17_tests/tests1.rs
index 7529f9f..a832ce0 100644
--- a/exercises/17_tests/tests1.rs
+++ b/exercises/17_tests/tests1.rs
@@ -13,11 +13,12 @@ fn main() {
 mod tests {
     // TODO: Import `is_even`. You can use a wildcard to import everything in
     // the outer module.
+    use super::is_even;
 
     #[test]
     fn you_can_assert() {
         // TODO: Test the function `is_even` with some values.
-        assert!();
-        assert!();
+        assert!(is_even(12));
+        assert!(!is_even(13));
     }
 }
diff --git a/exercises/17_tests/tests2.rs b/exercises/17_tests/tests2.rs
index 0c6573e..52faa7b 100644
--- a/exercises/17_tests/tests2.rs
+++ b/exercises/17_tests/tests2.rs
@@ -15,9 +15,9 @@ mod tests {
     #[test]
     fn you_can_assert_eq() {
         // TODO: Test the function `power_of_2` with some values.
-        assert_eq!();
-        assert_eq!();
-        assert_eq!();
-        assert_eq!();
+        assert_eq!(power_of_2(0), 1);
+        assert_eq!(power_of_2(1), 2);
+        assert_eq!(power_of_2(2), 4);
+        assert_eq!(power_of_2(3), 8);
     }
 }
diff --git a/exercises/17_tests/tests3.rs b/exercises/17_tests/tests3.rs
index 822184e..085bb62 100644
--- a/exercises/17_tests/tests3.rs
+++ b/exercises/17_tests/tests3.rs
@@ -29,13 +29,14 @@ mod tests {
         // TODO: This test should check if the rectangle has the size that we
         // pass to its constructor.
         let rect = Rectangle::new(10, 20);
-        assert_eq!(todo!(), 10); // Check width
-        assert_eq!(todo!(), 20); // Check height
+        assert_eq!(rect.width, 10); // Check width
+        assert_eq!(rect.height, 20); // Check height
     }
 
     // TODO: This test should check if the program panics when we try to create
     // a rectangle with negative width.
     #[test]
+    #[should_panic]
     fn negative_width() {
         let _rect = Rectangle::new(-10, 10);
     }
@@ -43,6 +44,7 @@ mod tests {
     // TODO: This test should check if the program panics when we try to create
     // a rectangle with negative height.
     #[test]
+    #[should_panic]
     fn negative_height() {
         let _rect = Rectangle::new(10, -10);
     }
diff --git a/exercises/18_iterators/iterators1.rs b/exercises/18_iterators/iterators1.rs
index ca937ed..71d8112 100644
--- a/exercises/18_iterators/iterators1.rs
+++ b/exercises/18_iterators/iterators1.rs
@@ -13,13 +13,13 @@ mod tests {
         let my_fav_fruits = ["banana", "custard apple", "avocado", "peach", "raspberry"];
 
         // TODO: Create an iterator over the array.
-        let mut fav_fruits_iterator = todo!();
+        let mut fav_fruits_iterator = my_fav_fruits.iter();
 
         assert_eq!(fav_fruits_iterator.next(), Some(&"banana"));
-        assert_eq!(fav_fruits_iterator.next(), todo!()); // TODO: Replace `todo!()`
+        assert_eq!(fav_fruits_iterator.next(), Some(&"custard apple")); // TODO: Replace `todo!()`
         assert_eq!(fav_fruits_iterator.next(), Some(&"avocado"));
-        assert_eq!(fav_fruits_iterator.next(), todo!()); // TODO: Replace `todo!()`
+        assert_eq!(fav_fruits_iterator.next(), Some(&"peach")); // TODO: Replace `todo!()`
         assert_eq!(fav_fruits_iterator.next(), Some(&"raspberry"));
-        assert_eq!(fav_fruits_iterator.next(), todo!()); // TODO: Replace `todo!()`
+        assert_eq!(fav_fruits_iterator.next(), None); // TODO: Replace `todo!()`
     }
 }
diff --git a/exercises/18_iterators/iterators2.rs b/exercises/18_iterators/iterators2.rs
index 5903e65..093c709 100644
--- a/exercises/18_iterators/iterators2.rs
+++ b/exercises/18_iterators/iterators2.rs
@@ -5,9 +5,10 @@
 // "hello" -> "Hello"
 fn capitalize_first(input: &str) -> String {
     let mut chars = input.chars();
+
     match chars.next() {
         None => String::new(),
-        Some(first) => todo!(),
+        Some(first) => first.to_uppercase().chain(chars).collect(),
     }
 }
 
@@ -15,14 +16,14 @@ fn capitalize_first(input: &str) -> String {
 // Return a vector of strings.
 // ["hello", "world"] -> ["Hello", "World"]
 fn capitalize_words_vector(words: &[&str]) -> Vec<String> {
-    // ???
+    words.iter().map(|word| capitalize_first(word)).collect()
 }
 
 // TODO: Apply the `capitalize_first` function again to a slice of string
 // slices. Return a single string.
 // ["hello", " ", "world"] -> "Hello World"
 fn capitalize_words_string(words: &[&str]) -> String {
-    // ???
+    words.iter().map(|word| capitalize_first(word)).collect()
 }
 
 fn main() {
diff --git a/exercises/18_iterators/iterators3.rs b/exercises/18_iterators/iterators3.rs
index dce0905..55f8292 100644
--- a/exercises/18_iterators/iterators3.rs
+++ b/exercises/18_iterators/iterators3.rs
@@ -11,21 +11,36 @@ enum DivisionError {
 // TODO: Calculate `a` divided by `b` if `a` is evenly divisible by `b`.
 // Otherwise, return a suitable error.
 fn divide(a: i64, b: i64) -> Result<i64, DivisionError> {
-    todo!();
+    match (a, b) {
+        (_, 0) => Err(DivisionError::DivideByZero),
+        (a, b) if a == i64::MIN && b == -1 => Err(DivisionError::IntegerOverflow),
+        (a, b) if a % b != 0 => Err(DivisionError::NotDivisible),
+        (a, b) => Ok(a / b),
+    }
 }
 
 // TODO: Add the correct return type and complete the function body.
 // Desired output: `Ok([1, 11, 1426, 3])`
-fn result_with_list() {
+fn result_with_list() -> Result<Vec<i64>, DivisionError> {
     let numbers = [27, 297, 38502, 81];
-    let division_results = numbers.into_iter().map(|n| divide(n, 27));
+    let result: Vec<i64> = numbers
+        .into_iter()
+        .map(|n| divide(n, 27))
+        .collect::<Result<Vec<i64>, DivisionError>>()?;
+
+    Ok(result)
 }
 
 // TODO: Add the correct return type and complete the function body.
 // Desired output: `[Ok(1), Ok(11), Ok(1426), Ok(3)]`
-fn list_of_results() {
+fn list_of_results() -> Vec<Result<i64, DivisionError>> {
     let numbers = [27, 297, 38502, 81];
-    let division_results = numbers.into_iter().map(|n| divide(n, 27));
+    let division_results: Vec<Result<i64, DivisionError>> = numbers
+        .into_iter()
+        .map(|n| divide(n, 27))
+        .collect::<Vec<Result<i64, DivisionError>>>();
+
+    division_results
 }
 
 fn main() {
diff --git a/exercises/18_iterators/iterators4.rs b/exercises/18_iterators/iterators4.rs
index c296f0e..c6efd9b 100644
--- a/exercises/18_iterators/iterators4.rs
+++ b/exercises/18_iterators/iterators4.rs
@@ -10,6 +10,7 @@ fn factorial(num: u64) -> u64 {
     // - additional variables
     // For an extra challenge, don't use:
     // - recursion
+    (1..=num).fold(1, |acc, e| acc * e)
 }
 
 fn main() {
diff --git a/exercises/18_iterators/iterators5.rs b/exercises/18_iterators/iterators5.rs
index 7e434cc..6b09665 100644
--- a/exercises/18_iterators/iterators5.rs
+++ b/exercises/18_iterators/iterators5.rs
@@ -28,6 +28,9 @@ fn count_for(map: &HashMap<String, Progress>, value: Progress) -> usize {
 fn count_iterator(map: &HashMap<String, Progress>, value: Progress) -> usize {
     // `map` is a hash map with `String` keys and `Progress` values.
     // map = { "variables1": Complete, "from_str": None, … }
+    map.values()
+        .filter(|excercise| **excercise == value)
+        .count()
 }
 
 fn count_collection_for(collection: &[HashMap<String, Progress>], value: Progress) -> usize {
@@ -48,6 +51,11 @@ fn count_collection_iterator(collection: &[HashMap<String, Progress>], value: Pr
     // `collection` is a slice of hash maps.
     // collection = [{ "variables1": Complete, "from_str": None, … },
     //               { "variables2": Complete, … }, … ]
+    collection
+        .iter()
+        .flatten()
+        .filter(|excercise| *excercise.1 == value)
+        .count()
 }
 
 fn main() {
diff --git a/exercises/19_smart_pointers/arc1.rs b/exercises/19_smart_pointers/arc1.rs
index 6bb860f..a5b9467 100644
--- a/exercises/19_smart_pointers/arc1.rs
+++ b/exercises/19_smart_pointers/arc1.rs
@@ -23,13 +23,13 @@ fn main() {
     let numbers: Vec<_> = (0..100u32).collect();
 
     // TODO: Define `shared_numbers` by using `Arc`.
-    // let shared_numbers = ???;
+    let shared_numbers = Arc::new(numbers);
 
     let mut join_handles = Vec::new();
 
     for offset in 0..8 {
         // TODO: Define `child_numbers` using `shared_numbers`.
-        // let child_numbers = ???;
+        let child_numbers = Arc::clone(&shared_numbers);
 
         let handle = thread::spawn(move || {
             let sum: u32 = child_numbers.iter().filter(|&&n| n % 8 == offset).sum();
diff --git a/exercises/19_smart_pointers/box1.rs b/exercises/19_smart_pointers/box1.rs
index d70e1c3..68ea288 100644
--- a/exercises/19_smart_pointers/box1.rs
+++ b/exercises/19_smart_pointers/box1.rs
@@ -12,18 +12,18 @@
 // TODO: Use a `Box` in the enum definition to make the code compile.
 #[derive(PartialEq, Debug)]
 enum List {
-    Cons(i32, List),
+    Cons(i32, Box<List>),
     Nil,
 }
 
 // TODO: Create an empty cons list.
 fn create_empty_list() -> List {
-    todo!()
+    List::Nil
 }
 
 // TODO: Create a non-empty cons list.
 fn create_non_empty_list() -> List {
-    todo!()
+    List::Cons(64, Box::new(List::Nil))
 }
 
 fn main() {
diff --git a/exercises/19_smart_pointers/cow1.rs b/exercises/19_smart_pointers/cow1.rs
index 1566500..0c9c1d6 100644
--- a/exercises/19_smart_pointers/cow1.rs
+++ b/exercises/19_smart_pointers/cow1.rs
@@ -39,7 +39,7 @@ mod tests {
         let mut input = Cow::from(&vec);
         abs_all(&mut input);
         // TODO: Replace `todo!()` with `Cow::Owned(_)` or `Cow::Borrowed(_)`.
-        assert!(matches!(input, todo!()));
+        assert!(matches!(input, Cow::Borrowed(_)));
     }
 
     #[test]
@@ -52,7 +52,7 @@ mod tests {
         let mut input = Cow::from(vec);
         abs_all(&mut input);
         // TODO: Replace `todo!()` with `Cow::Owned(_)` or `Cow::Borrowed(_)`.
-        assert!(matches!(input, todo!()));
+        assert!(matches!(input, Cow::Owned(_)));
     }
 
     #[test]
@@ -64,6 +64,6 @@ mod tests {
         let mut input = Cow::from(vec);
         abs_all(&mut input);
         // TODO: Replace `todo!()` with `Cow::Owned(_)` or `Cow::Borrowed(_)`.
-        assert!(matches!(input, todo!()));
+        assert!(matches!(input, Cow::Owned(_)));
     }
 }
diff --git a/exercises/19_smart_pointers/rc1.rs b/exercises/19_smart_pointers/rc1.rs
index ecd3438..ffce6e5 100644
--- a/exercises/19_smart_pointers/rc1.rs
+++ b/exercises/19_smart_pointers/rc1.rs
@@ -60,17 +60,17 @@ mod tests {
         jupiter.details();
 
         // TODO
-        let saturn = Planet::Saturn(Rc::new(Sun));
+        let saturn = Planet::Saturn(Rc::clone(&sun));
         println!("reference count = {}", Rc::strong_count(&sun)); // 7 references
         saturn.details();
 
         // TODO
-        let uranus = Planet::Uranus(Rc::new(Sun));
+        let uranus = Planet::Uranus(Rc::clone(&sun));
         println!("reference count = {}", Rc::strong_count(&sun)); // 8 references
         uranus.details();
 
         // TODO
-        let neptune = Planet::Neptune(Rc::new(Sun));
+        let neptune = Planet::Neptune(Rc::clone(&sun));
         println!("reference count = {}", Rc::strong_count(&sun)); // 9 references
         neptune.details();
 
@@ -91,13 +91,13 @@ mod tests {
         drop(mars);
         println!("reference count = {}", Rc::strong_count(&sun)); // 4 references
 
-        // TODO
+        drop(earth);
         println!("reference count = {}", Rc::strong_count(&sun)); // 3 references
 
-        // TODO
+        drop(venus);
         println!("reference count = {}", Rc::strong_count(&sun)); // 2 references
 
-        // TODO
+        drop(mercury);
         println!("reference count = {}", Rc::strong_count(&sun)); // 1 reference
 
         assert_eq!(Rc::strong_count(&sun), 1);
diff --git a/exercises/20_threads/threads1.rs b/exercises/20_threads/threads1.rs
index dbc64b1..a686224 100644
--- a/exercises/20_threads/threads1.rs
+++ b/exercises/20_threads/threads1.rs
@@ -20,10 +20,12 @@ fn main() {
         handles.push(handle);
     }
 
-    let mut results = Vec::new();
+    let mut results: Vec<_> = Vec::<_>::new();
+
     for handle in handles {
         // TODO: Collect the results of all threads into the `results` vector.
         // Use the `JoinHandle` struct which is returned by `thread::spawn`.
+        results.push(handle.join().unwrap())
     }
 
     if results.len() != 10 {
diff --git a/exercises/20_threads/threads2.rs b/exercises/20_threads/threads2.rs
index 7020cb9..b6a100b 100644
--- a/exercises/20_threads/threads2.rs
+++ b/exercises/20_threads/threads2.rs
@@ -2,24 +2,31 @@
 // work. But this time, the spawned threads need to be in charge of updating a
 // shared value: `JobStatus.jobs_done`
 
-use std::{sync::Arc, thread, time::Duration};
+use std::{
+    sync::{Arc, Mutex},
+    thread,
+    time::Duration,
+};
 
+#[derive(Debug)]
 struct JobStatus {
     jobs_done: u32,
 }
 
 fn main() {
     // TODO: `Arc` isn't enough if you want a **mutable** shared state.
-    let status = Arc::new(JobStatus { jobs_done: 0 });
+    let status = Arc::new(Mutex::new(JobStatus { jobs_done: 0 }));
 
     let mut handles = Vec::new();
     for _ in 0..10 {
         let status_shared = Arc::clone(&status);
+
         let handle = thread::spawn(move || {
             thread::sleep(Duration::from_millis(250));
 
             // TODO: You must take an action before you update a shared value.
-            status_shared.jobs_done += 1;
+            let mut acquired_status = status_shared.lock().unwrap();
+            acquired_status.jobs_done += 1;
         });
         handles.push(handle);
     }
@@ -30,5 +37,7 @@ fn main() {
     }
 
     // TODO: Print the value of `JobStatus.jobs_done`.
-    println!("Jobs done: {}", todo!());
+    let mutex = Arc::try_unwrap(status).unwrap();
+    let job_status = mutex.into_inner().unwrap();
+    println!("Jobs done: {}", job_status.jobs_done);
 }
diff --git a/exercises/20_threads/threads3.rs b/exercises/20_threads/threads3.rs
index 6d16bd9..994d985 100644
--- a/exercises/20_threads/threads3.rs
+++ b/exercises/20_threads/threads3.rs
@@ -17,18 +17,23 @@ impl Queue {
 fn send_tx(q: Queue, tx: mpsc::Sender<u32>) {
     // TODO: We want to send `tx` to both threads. But currently, it is moved
     // into the first thread. How could you solve this problem?
+
+    let transmission = tx.clone();
+
     thread::spawn(move || {
         for val in q.first_half {
             println!("Sending {val:?}");
-            tx.send(val).unwrap();
+            transmission.send(val).unwrap();
             thread::sleep(Duration::from_millis(250));
         }
     });
 
+    let transmission = tx.clone();
+
     thread::spawn(move || {
         for val in q.second_half {
             println!("Sending {val:?}");
-            tx.send(val).unwrap();
+            transmission.send(val).unwrap();
             thread::sleep(Duration::from_millis(250));
         }
     });
diff --git a/exercises/21_macros/macros1.rs b/exercises/21_macros/macros1.rs
index fb3c3ff..fb550f9 100644
--- a/exercises/21_macros/macros1.rs
+++ b/exercises/21_macros/macros1.rs
@@ -6,5 +6,5 @@ macro_rules! my_macro {
 
 fn main() {
     // TODO: Fix the macro call.
-    my_macro();
+    my_macro!();
 }
diff --git a/exercises/21_macros/macros2.rs b/exercises/21_macros/macros2.rs
index 2d9dec7..f310a0b 100644
--- a/exercises/21_macros/macros2.rs
+++ b/exercises/21_macros/macros2.rs
@@ -1,10 +1,10 @@
-fn main() {
-    my_macro!();
-}
-
 // TODO: Fix the compiler error by moving the whole definition of this macro.
 macro_rules! my_macro {
     () => {
         println!("Check out my macro!");
     };
 }
+
+fn main() {
+    my_macro!();
+}
diff --git a/exercises/21_macros/macros3.rs b/exercises/21_macros/macros3.rs
index 9537494..7b2e72b 100644
--- a/exercises/21_macros/macros3.rs
+++ b/exercises/21_macros/macros3.rs
@@ -1,6 +1,7 @@
 // TODO: Fix the compiler error without taking the macro definition out of this
 // module.
 mod macros {
+    #[macro_export]
     macro_rules! my_macro {
         () => {
             println!("Check out my macro!");
diff --git a/exercises/21_macros/macros4.rs b/exercises/21_macros/macros4.rs
index 9d77f6a..3396f0d 100644
--- a/exercises/21_macros/macros4.rs
+++ b/exercises/21_macros/macros4.rs
@@ -3,7 +3,7 @@
 macro_rules! my_macro {
     () => {
         println!("Check out my macro!");
-    }
+    };
     ($val:expr) => {
         println!("Look at this other macro: {}", $val);
     }
diff --git a/exercises/22_clippy/clippy1.rs b/exercises/22_clippy/clippy1.rs
index 7165da4..4c4b52a 100644
--- a/exercises/22_clippy/clippy1.rs
+++ b/exercises/22_clippy/clippy1.rs
@@ -6,7 +6,7 @@
 
 fn main() {
     // TODO: Fix the Clippy lint in this line.
-    let pi = 3.14;
+    let pi = std::f32::consts::PI;
     let radius: f32 = 5.0;
 
     let area = pi * radius.powi(2);
diff --git a/exercises/22_clippy/clippy2.rs b/exercises/22_clippy/clippy2.rs
index 8cfe6f8..4605ee9 100644
--- a/exercises/22_clippy/clippy2.rs
+++ b/exercises/22_clippy/clippy2.rs
@@ -1,8 +1,9 @@
 fn main() {
     let mut res = 42;
     let option = Some(12);
+
     // TODO: Fix the Clippy lint.
-    for x in option {
+    if let Some(x) = option {
         res += x;
     }
 
diff --git a/exercises/22_clippy/clippy3.rs b/exercises/22_clippy/clippy3.rs
index 7a3cb39..276d027 100644
--- a/exercises/22_clippy/clippy3.rs
+++ b/exercises/22_clippy/clippy3.rs
@@ -7,23 +7,23 @@ fn main() {
     let my_option: Option<&str> = None;
     // Assume that you don't know the value of `my_option`.
     // In the case of `Some`, we want to print its value.
-    if my_option.is_none() {
-        println!("{}", my_option.unwrap());
+    if let Some(my_option) = my_option {
+        println!("{}", my_option);
     }
 
     let my_arr = &[
-        -1, -2, -3
+        -1, -2, -3,
         -4, -5, -6
     ];
     println!("My array! Here it is: {my_arr:?}");
 
-    let my_empty_vec = vec![1, 2, 3, 4, 5].resize(0, 5);
+    let my_empty_vec = ();
+    vec![1, 2, 3, 4, 5].resize(0, 5);
     println!("This Vec is empty, see? {my_empty_vec:?}");
 
     let mut value_a = 45;
     let mut value_b = 66;
     // Let's swap these two!
-    value_a = value_b;
-    value_b = value_a;
+    std::mem::swap(&mut value_a, &mut value_b);
     println!("value a: {value_a}; value b: {value_b}");
 }
diff --git a/exercises/23_conversions/as_ref_mut.rs b/exercises/23_conversions/as_ref_mut.rs
index d7892dd..c13b3c7 100644
--- a/exercises/23_conversions/as_ref_mut.rs
+++ b/exercises/23_conversions/as_ref_mut.rs
@@ -5,20 +5,22 @@
 // Obtain the number of bytes (not characters) in the given argument
 // (`.len()` returns the number of bytes in a string).
 // TODO: Add the `AsRef` trait appropriately as a trait bound.
-fn byte_counter<T>(arg: T) -> usize {
+fn byte_counter<T: AsRef<str>>(arg: T) -> usize {
     arg.as_ref().len()
 }
 
 // Obtain the number of characters (not bytes) in the given argument.
 // TODO: Add the `AsRef` trait appropriately as a trait bound.
-fn char_counter<T>(arg: T) -> usize {
+fn char_counter<T: AsRef<str>>(arg: T) -> usize {
     arg.as_ref().chars().count()
 }
 
 // Squares a number using `as_mut()`.
 // TODO: Add the appropriate trait bound.
-fn num_sq<T>(arg: &mut T) {
+fn num_sq<T: AsMut<u32>>(arg: &mut T) {
     // TODO: Implement the function body.
+    let val = *arg.as_mut();
+    *arg.as_mut() = val * val;
 }
 
 fn main() {
diff --git a/exercises/23_conversions/from_into.rs b/exercises/23_conversions/from_into.rs
index bc2783a..97b1caf 100644
--- a/exercises/23_conversions/from_into.rs
+++ b/exercises/23_conversions/from_into.rs
@@ -34,7 +34,18 @@ impl Default for Person {
 // 5. Parse the second element from the split operation into a `u8` as the age.
 // 6. If parsing the age fails, return the default of `Person`.
 impl From<&str> for Person {
-    fn from(s: &str) -> Self {}
+    fn from(s: &str) -> Self {
+        match s.split(",").collect::<Vec<&str>>().as_slice() {
+            [name, age] if (!name.is_empty() && !age.is_empty()) => match age.parse::<u8>() {
+                Ok(age) => Person {
+                    name: name.to_string(),
+                    age,
+                },
+                Err(_) => Person::default(),
+            },
+            _ => Person::default(),
+        }
+    }
 }
 
 fn main() {
diff --git a/exercises/23_conversions/from_str.rs b/exercises/23_conversions/from_str.rs
index ec6d3fd..e2682b6 100644
--- a/exercises/23_conversions/from_str.rs
+++ b/exercises/23_conversions/from_str.rs
@@ -41,7 +41,19 @@ enum ParsePersonError {
 impl FromStr for Person {
     type Err = ParsePersonError;
 
-    fn from_str(s: &str) -> Result<Self, Self::Err> {}
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s.split(",").collect::<Vec<&str>>().as_slice() {
+            [name, age] if (!name.is_empty()) => match age.parse::<u8>() {
+                Ok(age) => Ok(Person {
+                    name: name.to_string(),
+                    age,
+                }),
+                Err(err) => Err(ParsePersonError::ParseInt(err)),
+            },
+            ["", _] => Err(ParsePersonError::NoName),
+            _ => Err(ParsePersonError::BadLen),
+        }
+    }
 }
 
 fn main() {
diff --git a/exercises/23_conversions/try_from_into.rs b/exercises/23_conversions/try_from_into.rs
index f3ae80a..b041f31 100644
--- a/exercises/23_conversions/try_from_into.rs
+++ b/exercises/23_conversions/try_from_into.rs
@@ -28,14 +28,45 @@ enum IntoColorError {
 impl TryFrom<(i16, i16, i16)> for Color {
     type Error = IntoColorError;
 
-    fn try_from(tuple: (i16, i16, i16)) -> Result<Self, Self::Error> {}
+    fn try_from(tuple: (i16, i16, i16)) -> Result<Self, Self::Error> {
+        match tuple {
+            (red, green, blue)
+                if (0..=255).contains(&red)
+                    && (0..=255).contains(&green)
+                    && (0..=255).contains(&blue) =>
+            {
+                Ok(Color {
+                    red: red as u8,
+                    green: green as u8,
+                    blue: blue as u8,
+                })
+            }
+            _ => Err(IntoColorError::IntConversion),
+        }
+    }
 }
 
 // TODO: Array implementation.
 impl TryFrom<[i16; 3]> for Color {
     type Error = IntoColorError;
 
-    fn try_from(arr: [i16; 3]) -> Result<Self, Self::Error> {}
+    fn try_from(arr: [i16; 3]) -> Result<Self, Self::Error> {
+        match arr.as_slice() {
+            [red, green, blue] => {
+                if (0..=255).contains(red) && (0..=255).contains(green) && (0..=255).contains(blue)
+                {
+                    Ok(Color {
+                        red: *red as u8,
+                        green: *green as u8,
+                        blue: *blue as u8,
+                    })
+                } else {
+                    Err(IntoColorError::IntConversion)
+                }
+            }
+            _ => Err(IntoColorError::BadLen),
+        }
+    }
 }
 
 // TODO: Slice implementation.
@@ -43,7 +74,23 @@ impl TryFrom<[i16; 3]> for Color {
 impl TryFrom<&[i16]> for Color {
     type Error = IntoColorError;
 
-    fn try_from(slice: &[i16]) -> Result<Self, Self::Error> {}
+    fn try_from(slice: &[i16]) -> Result<Self, Self::Error> {
+        match slice {
+            [red, green, blue] => {
+                if (0..=255).contains(red) && (0..=255).contains(green) && (0..=255).contains(blue)
+                {
+                    Ok(Color {
+                        red: *red as u8,
+                        green: *green as u8,
+                        blue: *blue as u8,
+                    })
+                } else {
+                    Err(IntoColorError::IntConversion)
+                }
+            }
+            _ => Err(IntoColorError::BadLen),
+        }
+    }
 }
 
 fn main() {
diff --git a/exercises/23_conversions/using_as.rs b/exercises/23_conversions/using_as.rs
index c131d1f..dff453b 100644
--- a/exercises/23_conversions/using_as.rs
+++ b/exercises/23_conversions/using_as.rs
@@ -5,7 +5,7 @@
 fn average(values: &[f64]) -> f64 {
     let total = values.iter().sum::<f64>();
     // TODO: Make a conversion before dividing.
-    total / values.len()
+    total / values.len() as f64
 }
 
 fn main() {
diff --git a/exercises/quizzes/quiz2.rs b/exercises/quizzes/quiz2.rs
index 2cddba9..d12cafd 100644
--- a/exercises/quizzes/quiz2.rs
+++ b/exercises/quizzes/quiz2.rs
@@ -27,7 +27,21 @@ mod my_module {
     use super::Command;
 
     // TODO: Complete the function as described above.
-    // pub fn transformer(input: ???) -> ??? { ??? }
+    pub fn transformer(input: Vec<(String, Command)>) -> Vec<String> {
+        let mut output: Vec<String> = Vec::new();
+
+        for (string, command) in input {
+            match command {
+                Command::Uppercase => output.push(string.to_uppercase()),
+                Command::Trim => output.push(string.trim().into()),
+                Command::Append(number_of_times_bar_will_be_added) => {
+                    output.push(string + &"bar".repeat(number_of_times_bar_will_be_added))
+                }
+            }
+        }
+
+        output
+    }
 }
 
 fn main() {
@@ -37,8 +51,8 @@ fn main() {
 #[cfg(test)]
 mod tests {
     // TODO: What do we need to import to have `transformer` in scope?
-    // use ???;
     use super::Command;
+    use super::my_module::transformer;
 
     #[test]
     fn it_works() {
diff --git a/exercises/quizzes/quiz3.rs b/exercises/quizzes/quiz3.rs
index c877c5f..4fc72ce 100644
--- a/exercises/quizzes/quiz3.rs
+++ b/exercises/quizzes/quiz3.rs
@@ -10,16 +10,17 @@
 //
 // Make the necessary code changes in the struct `ReportCard` and the impl
 // block to support alphabetical report cards in addition to numerical ones.
+use std::fmt::Display;
 
 // TODO: Adjust the struct as described above.
-struct ReportCard {
-    grade: f32,
+struct ReportCard<G: Display> {
+    grade: G,
     student_name: String,
     student_age: u8,
 }
 
 // TODO: Adjust the impl block as described above.
-impl ReportCard {
+impl<G: Display> ReportCard<G> {
     fn print(&self) -> String {
         format!(
             "{} ({}) - achieved a grade of {}",