Ответ:

  1. \(268+349=268+300+49=568+49=617\).
  2. \(717+285=717+200+85=917+85=1002\).
  3. \(846+178=846+100+78=946+78=1024\).
  4. \(456+278=456+200+78=656+78=734\).
  5. \(175+698=175+600+98=775+98=873\).
  6. \(426+378=426+300+78=726+78=804\).
  7. \(594+286=594+200+86=794+86=880\).
  8. \(708+196=708+100+96=808+96=904\).