input: Write a python function to check if a given number is greater than or equal to 3.
  assert check_number(3) == 'x is greater than or equal to 3'
  assert check_number(5) == 'x is greater than or equal to 3'
  assert check_number(2) != 'x is greater than or equal to 3'
output: def check_number(x):
      if x >= 3:
          return 'x is greater than or equal to 3'
      else:
          return 'x is less than 3'