diff --git a/Lesson01/Lesson01/Program.cs b/Lesson01/Lesson01/Program.cs
index 2774e62..77dacd2 100644
--- a/Lesson01/Lesson01/Program.cs
+++ b/Lesson01/Lesson01/Program.cs
@@ -7,11 +7,9 @@ static void Main(string[] args)
             Console.WriteLine("Hello, World!");
         }
 
-        // Homework
-        // Complete the following method
         public static int Add(int a, int b)
         {
-            return 0;
+            return a + b;
         }
     }
 }
\ No newline at end of file
diff --git a/Lesson04/Lesson04.sln b/Lesson04/Lesson04.sln
new file mode 100644
index 0000000..b4af16e
--- /dev/null
+++ b/Lesson04/Lesson04.sln
@@ -0,0 +1,25 @@
+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 17
+VisualStudioVersion = 17.6.33815.320
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Lesson04", "Lesson04\Lesson04.csproj", "{2BD7DB44-DD50-4842-8301-2355386ED7AF}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{2BD7DB44-DD50-4842-8301-2355386ED7AF}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{2BD7DB44-DD50-4842-8301-2355386ED7AF}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{2BD7DB44-DD50-4842-8301-2355386ED7AF}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{2BD7DB44-DD50-4842-8301-2355386ED7AF}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {69432ABB-02AF-4CEB-ADBD-A1736AFB0F56}
+	EndGlobalSection
+EndGlobal
diff --git a/Lesson04/Lesson04/Lesson04.csproj b/Lesson04/Lesson04/Lesson04.csproj
new file mode 100644
index 0000000..f02677b
--- /dev/null
+++ b/Lesson04/Lesson04/Lesson04.csproj
@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net7.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>
diff --git a/Lesson04/Lesson04/Program.cs b/Lesson04/Lesson04/Program.cs
new file mode 100644
index 0000000..afbfe1c
--- /dev/null
+++ b/Lesson04/Lesson04/Program.cs
@@ -0,0 +1,97 @@
+namespace Lesson04
+{
+    internal class Program
+    {
+        public delegate bool Predicate1<T>(int t, int max);
+
+        static void Main(string[] args)
+        {
+            int[] numbers = { 1, 9, 3, 4, -5, -6, -7, 8 };
+            Where(numbers, NegativeNumbers);
+        }
+        static void Count(int[] number, Predicate<int> predicate)
+        {
+            int counter = 0;
+            foreach (int i in number)
+            {
+                if (predicate(i))
+                {
+                    counter++;
+                }
+            }
+            Console.WriteLine(counter);
+        }
+        static void Max(int[] number, Predicate1<int> predicate)
+        {
+            int max = 0;
+            for (int i = 0; i < number.Length; ++i)
+            {
+                if (predicate(max, number[i]))
+                {
+                    max = number[i];
+                }
+            }
+            Console.WriteLine(max);
+        }
+        static void Min(int[] number, Predicate1<int> predicate)
+        {
+            int min = number[0];
+            for (int i = 1; i < number.Length - 1; ++i)
+            {
+                if (predicate(min, number[i]))
+                {
+                    min = number[i];
+                }
+            }
+            Console.WriteLine(min);
+        }
+        static void Where(int[] number, Predicate<int> predicate)
+        {
+            List<int> numbers = new List<int>();
+            for (int i = 0; i < number.Length; ++i)
+            {
+                if (predicate(number[i]))
+                {
+                    numbers.Add(number[i]);
+                }
+            }
+            foreach (int i in numbers)
+            {
+                Console.WriteLine(i);
+            }
+        }
+        static bool NegativeNumbers(int num)
+        {
+            if (num < 0)
+            {
+                return true;
+            }
+            return false;
+        }
+        static bool MinMax(int num1, int max)
+        {
+            if (num1 < max)
+            {
+                return true;
+            }
+            return false;
+        }
+        static bool Positive(int number)
+        {
+            if (number < 0)
+            {
+                return false;
+            }
+            return true;
+        }
+        static bool MinNumber(int number, int min)
+        {
+            if (min < number)
+            {
+                return true;
+            }
+            return false;
+        }
+    }
+}
+