Ответ:

  1. \(248 + 407 = 655\). Проверка: \(655 - 407 = 248\).
  2. \(420 - 176 = 244\). Проверка: \(244 + 176 = 420\).
  3. \(302 - 254 = 48\). Проверка: \(48 + 254 = 302\).
  4. \(703 + 94 + 12 = 797 + 12 = 809\). Проверка: \(809 - 12 - 94 = 703\).
  5. \(760 - (120 + 80) + 60 = 760 - 200 + 60 = 620\).
  6. \(500 - (270 + 130) - 1 = 500 - 400 - 1 = 99\).
  7. \(120 : (60 : 6) : 2 = 120 : 10 : 2 = 12 : 2 = 6\).
  8. \(90 : (45 : 9) \cdot 2 = 90 : 5 \cdot 2 = 18 \cdot 2 = 36\).