Ответ:

  1. (13 + p) + 87 = p + (13 + 87) = p + 100.
  2. 214 + (186 + k) = (214 + 186) + k = 400 + k.
  3. x + 349 + 251 = x + 600 = x + 600.
  4. 4985 + y + 17 115 = 22 100 + y = 22 100 + y.