public void IncreaseBy(Rational other)
 {
     int den = this.denominator * other.denominator;
     int num = (this.denominator * other.numerator) + (this.numerator * other.denominator);
     this.denominator = den;
     this.numerator = num;
 }
        static void Main(string[] args)
        {
            Rational rational1 = new Rational(1, 2);
            Rational rational2 = new Rational(2, 3);
            Rational rational3 = new Rational(1, 3);
            Rational rational4 = new Rational(2, 5);

            Console.WriteLine("Rational 1: {0}\nRational 2: {1}\nRational 3: {2}\nRational 4: {3}", rational1, rational2, rational3, rational4);

            Console.Write("\nRational2 + Rational1: {0} {1} {2}", rational2, "+", rational1);
            rational2.IncreaseBy(rational1);
            Console.Write(" = {0}", rational2);

            Console.Write("\nRational4 - Rational3: {0} {1} {2}", rational4, "-", rational3);
            rational4.DecreaseBy(rational3);
            Console.Write(" = {0}", rational4);

            Console.Write("\nRational1 + Rational3: {0} {1} {2}", rational1, "+", rational3);
            rational1.IncreaseBy(rational3);
            Console.Write(" = {0}", rational1);

            Console.ReadLine();
        }