Ответ:

  1. 16 - 9 + 8 = 7 + 8 = 15
  2. 17 - 9 + 5 = 8 + 5 = 13
  3. 18 - (12 - 4) = 18 - 8 = 10
  4. 12 - (3 + 9) = 12 - 12 = 0
  5. 18 - 9 + 5 = 9 + 5 = 14
  6. 15 - 7 + 8 = 8 + 8 = 16