Ответ:

  1. 68 + 52 = 68 + 50 + 2 = 120.
  2. 84 + 47 = 84 + 40 + 7 = 131.
  3. 48 + 38 = 48 + 30 + 8 = 86.
  4. 123 + 87 = 123 + 80 + 7 = 210.
  5. 268 + 99 = 268 + 100 − 1 = 367.
  6. 957 + 40 = 997.
  7. 689 + 64 = 689 + 60 + 4 = 753.
  8. 778 + 903 = 778 + 900 + 3 = 1681.
  9. 204 + 266 = 204 + 200 + 66 = 470.
  10. 609 + 337 = 609 + 300 + 37 = 946.