input: Write a python function to divide two numbers and return both the quotient and the remainder.
  assert divide(15, 4) == (3, 3)
  assert divide(20, 6) == (3, 2)
  assert divide(9, 3) == (3, 0)
output: def divide(a, b):
      quotient = a // b
      remainder = a % b
      return quotient, remainder