docs: public Rational subtract(Rational value)
      {
          if (denominator == value.getDenominator())
          {
              return new Rational(numerator - value.getNumerator(), denominator);
          }
          else
          {
              return new Rational(numerator * value.getDenominator() - value.getNumerator() * denominator,
                                  denominator * value.getDenominator());
          }
      }