input: Write a python function to find numbers greater than a given number n in a list.
  assert greater_than_n([3,4,5,6,7], 5) == [6, 7]
  assert greater_than_n([1, 2, 3, 4, 5], 2) == [3, 4, 5]
  assert greater_than_n([10, 20, 30, 40, 50], 25) == [30, 40, 50]
output: def greater_than_n(lst, n):
      return [x for x in lst if x > n]