Ответ:

  1. 12 − 8 + 4 = 4 + 4 = 8.

  2. 12 − (7 − 3) = 12 − 4 = 8.

  3. 54 − 50 + 60 = 4 + 60 = 64.

  4. 8 + (54 − 60) = 8 + (−6) = 2.

  5. 80 + (5 − 2) = 80 + 3 = 83.

  6. (45 − 40) + 8 = 5 + 8 = 13.