static void Main()
{
ClsMaths obj = new ClsMaths();
Console.WriteLine(obj.Subtract(20, 10));
Console.ReadLine();
}
static void Main1()
{
int i = 100, j = 200;
j = i.Add(5);
j.PrintInt(); //=>
ExtensionMethodsClass.PrintInt(j);
string s = "a";
s.DoSomethingForTheBaseClass();
i.DoSomethingForTheBaseClass();
ClsMaths objMath = new ClsMaths();
Console.WriteLine(objMath.Subtract(20, 10));
Console.ReadLine();
}