static void Main(string[] args)
        {
            CalculatorVersionTwo calculator = new CalculatorVersionTwo();

            int x = 20;

            Console.WriteLine(x.IsGreaterThan(10));
            Console.WriteLine(x.IsLessThan(5));
        }
 public static string ConcatStrings(this CalculatorVersionTwo calculator, string firstString, string secondString)
 {
     return(firstString + secondString);
 }