Ответ:

  1. 53 + 888 = 888 + 50 + 3 = 941.
  2. 171 + 353 = 171 + 300 + 50 + 3 = 524.
  3. 979 − 791 = 979 − 700 − 90 − 1 = 188.
  4. 718 + 173 = 718 + 100 + 70 + 3 = 891.
  5. 238 + 11 = 238 + 10 + 1 = 249.