input: Write a python function to add a number to each word in a given text using split and join methods.
  assert add_num(2, "5 10 15 20") == "7 12 17 22"
  assert add_num(3, "1 2 3 4") == "4 5 6 7"
  assert add_num(0, "9 8 7 6") == "9 8 7 6"
output: def add_num(num, text):
      return ' '.join(str(int(word) + num) for word in text.split())