public static RatNum add(RatNum x, RatNum y, int k)
{
IntNum x_num = x.numerator();
IntNum x_den = x.denominator();
IntNum y_num = y.numerator();
IntNum y_den = y.denominator();
if (IntNum.equals(x_den, y_den))
{
return(RatNum.make(IntNum.add(x_num, y_num, k), x_den));
}
return(RatNum.make(IntNum.add(IntNum.times(y_den, x_num),
IntNum.times(y_num, x_den), k),
IntNum.times(x_den, y_den)));
}