input: Write a function to reduce a fraction to its lowest terms.
  assert reduceFraction(12, 20) == (3, 5)
  assert reduceFraction(50, 100) == (1, 2)
  assert reduceFraction(8, 12) == (2, 3)
output: def reduceFraction(numerator, denominator):
      def gcd(a, b):
          while b:
              a, b = b, a % b
          return a
  
      greatest_common_divisor = gcd(numerator, denominator)
      return numerator // greatest_common_divisor, denominator // greatest_common_divisor