diff --git a/Sources/AngouriMath/AngouriMath/Convenience/SettingClass.cs b/Sources/AngouriMath/AngouriMath/Convenience/SettingClass.cs
index 308cdc13c..40a231b9d 100644
--- a/Sources/AngouriMath/AngouriMath/Convenience/SettingClass.cs
+++ b/Sources/AngouriMath/AngouriMath/Convenience/SettingClass.cs
@@ -158,7 +158,7 @@ internal sealed class KeyStack<TKey, TValue>
     {
         private readonly List<(TKey key, TValue value)> list = new();
 
-        internal TValue Peek() => list[list.Count - 1].value;
+        internal TValue Peek() => list[^1].value;
 
         internal bool Remove(TKey key)
         {
diff --git a/Sources/AngouriMath/AngouriMath/Functions/Boolean/TableSolver.cs b/Sources/AngouriMath/AngouriMath/Functions/Boolean/TableSolver.cs
index 208fbf95f..5ef389845 100644
--- a/Sources/AngouriMath/AngouriMath/Functions/Boolean/TableSolver.cs
+++ b/Sources/AngouriMath/AngouriMath/Functions/Boolean/TableSolver.cs
@@ -46,7 +46,7 @@ internal static bool Next(in Span<bool> states)
         /// <exception cref="WrongNumberOfArgumentsException"/>
         internal static Matrix? SolveTable(Entity expr, Variable[] variables)
         {
-            var count = expr.Vars.Count();
+            var count = expr.Vars.Count;
             // TODO: we probably also should verify the uniqueness of the given variables
             if (count != variables.Length)
                 throw new WrongNumberOfArgumentsException("Number of variables must equal number of variables in the expression");
@@ -67,7 +67,7 @@ internal static bool Next(in Span<bool> states)
 
         internal static Matrix? BuildTruthTable(Entity expr, Variable[] variables)
         {
-            var count = expr.Vars.Count();
+            var count = expr.Vars.Count;
             // TODO: we probably also should verify the uniqueness of the given variables
             if (count != variables.Length)
                 throw new WrongNumberOfArgumentsException("Number of variables must equal number of variables in the expression");
diff --git a/Sources/AngouriMath/AngouriMath/Functions/Compilation/IntoLinq/CompilationProtocol.cs b/Sources/AngouriMath/AngouriMath/Functions/Compilation/IntoLinq/CompilationProtocol.cs
index 78fa64bcf..4c93d97ca 100644
--- a/Sources/AngouriMath/AngouriMath/Functions/Compilation/IntoLinq/CompilationProtocol.cs
+++ b/Sources/AngouriMath/AngouriMath/Functions/Compilation/IntoLinq/CompilationProtocol.cs
@@ -258,8 +258,8 @@ private Expression HandlePiecewise(IEnumerable<Expression> en)
             }
             
             // last case
-            var expression = children[children.Length - 2];
-            var predicate = children[children.Length - 1];
+            var expression = children[^2];
+            var predicate = children[^1];
             var nan = ConvertNaN(maxType);
             
             (expression, nan) = EqualizeTypesIfAble(expression, nan);
diff --git a/Sources/AngouriMath/AngouriMath/Functions/Continuous/Solvers/EquationSolver.cs b/Sources/AngouriMath/AngouriMath/Functions/Continuous/Solvers/EquationSolver.cs
index f05e33d41..a1cc1d053 100644
--- a/Sources/AngouriMath/AngouriMath/Functions/Continuous/Solvers/EquationSolver.cs
+++ b/Sources/AngouriMath/AngouriMath/Functions/Continuous/Solvers/EquationSolver.cs
@@ -26,7 +26,7 @@ internal static Set Solve(Entity equation, Variable x)
 
             static Entity simplifier(Entity entity) => entity.InnerSimplified;
             static Entity evaluator(Entity entity) => entity.Evaled;
-            var factorizer = equation.Vars.Count() == 1 ? (Func<Entity, Entity>)evaluator : simplifier;
+            var factorizer = equation.Vars.Count == 1 ? (Func<Entity, Entity>)evaluator : simplifier;
 
 
             if (solutions is FiniteSet finiteSet)
@@ -75,7 +75,7 @@ internal static Set Solve(Entity equation, Variable x)
         /// </param>
         internal static List<List<Entity>> InSolveSystem(List<Entity> equations, ReadOnlySpan<Variable> vars)
         {
-            var var = vars[vars.Length - 1];
+            var var = vars[^1];
             if (equations.Count == 1)
                 return equations[0].InnerSimplified.SolveEquation(var) is FiniteSet els 
                        ? els.Select(sol => new List<Entity> { sol }).ToList()
diff --git a/Sources/AngouriMath/AngouriMath/Functions/Continuous/Solvers/EquationSolver/AnalyticalEquationSolver.cs b/Sources/AngouriMath/AngouriMath/Functions/Continuous/Solvers/EquationSolver/AnalyticalEquationSolver.cs
index 3f82d99db..527c08982 100644
--- a/Sources/AngouriMath/AngouriMath/Functions/Continuous/Solvers/EquationSolver/AnalyticalEquationSolver.cs
+++ b/Sources/AngouriMath/AngouriMath/Functions/Continuous/Solvers/EquationSolver/AnalyticalEquationSolver.cs
@@ -209,7 +209,7 @@ static Entity TryDowncast(Entity equation, Variable x, Entity root)
             // https://mathoverflow.net/a/28977
 
             // if nothing has been found so far
-            if (MathS.Settings.AllowNewton && expr.Vars.Count() == 1)
+            if (MathS.Settings.AllowNewton && expr.Vars.Count == 1)
                 return expr.SolveNt(x).Select(ent => TryDowncast(expr, x, ent)).ToSet();
 
             return Enumerable.Empty<Entity>().ToSet();
diff --git a/Sources/AngouriMath/AngouriMath/Functions/NumberTheory/Primes.cs b/Sources/AngouriMath/AngouriMath/Functions/NumberTheory/Primes.cs
index 8f8e9c6ea..ff12d80e5 100644
--- a/Sources/AngouriMath/AngouriMath/Functions/NumberTheory/Primes.cs
+++ b/Sources/AngouriMath/AngouriMath/Functions/NumberTheory/Primes.cs
@@ -58,7 +58,7 @@ static bool IsPrimeI(Integer num)
 
             static void AddPrimeC()
             {
-                var n = (primes[primes.Count - 1].cache + 2) ?? throw new AngouriBugException("It was supposed to be not null");
+                var n = (primes[^1].cache + 2) ?? throw new AngouriBugException("It was supposed to be not null");
                 while (!IsPrimeC(n))
                     n += 2;
                 primes.Add((n, n));
@@ -66,7 +66,7 @@ static void AddPrimeC()
 
             static void AddPrimeI()
             {
-                var n = (primes[primes.Count - 1].actual + 2) ?? throw new AngouriBugException("It was supposed to be not null");
+                var n = (primes[^1].actual + 2) ?? throw new AngouriBugException("It was supposed to be not null");
                 while (!IsPrimeI(n))
                     n += 2;
                 primes.Add((n, null));
diff --git a/Sources/Tests/UnitTests/Convenience/FromStringTest.cs b/Sources/Tests/UnitTests/Convenience/FromStringTest.cs
index 9a15054bb..57a8178a6 100644
--- a/Sources/Tests/UnitTests/Convenience/FromStringTest.cs
+++ b/Sources/Tests/UnitTests/Convenience/FromStringTest.cs
@@ -318,7 +318,7 @@ public void TestInequalityCompositionPrettySyntax(
         public void TestUnicodeVariablesParser(string exprRaw, string expectedName)
         {
             Entity actual = exprRaw;
-            var any = actual.Vars.First();
+            var any = actual.Vars[0];
             Assert.Equal(expectedName, any.Name);
         }