Ответ:

  1. \(42+14=56\); \(27+48=75\); \(31+17=48\).
  2. \(3\cdot8=24\); \(16:2=8\); \(21:3=7\).
  3. \(63:7=9\); \(6\cdot9=54\); \(4\cdot7=28\).