input: Write a python function to compute the average of a list of numbers provided by the user.
  assert averageNums([1, 2, 3]) == 2.0
  assert averageNums([10, 20, 30]) == 20.0
  assert averageNums([5.5, 4.5, 6.5]) == 5.5
output: def averageNums(nums):
      return sum(nums) / len(nums)