public static void Main()
Console.WriteLine("Hello World!");
Console.WriteLine("7+3=" + a);
Console.WriteLine("7-3=" + b);
Console.WriteLine("7*3=" + c);
Console.WriteLine("7/3=" + d);
Console.WriteLine("7.0/3.0=" + e);
Console.WriteLine("7%3=" + f);
Console.WriteLine("7+3*5=" + g);
Console.WriteLine("(7+3)*5=" + h);