Ответ:

  1. \(980-80-100=900-100=800\).

  2. \(640-40+200=600+200=800\).

  3. \(290+70=360\).

  4. \(680+50=730\).

  5. \(140\cdot6=840\).

  6. \(260\cdot3=780\).

  7. \(480:6=80\).

  8. \(360:9=40\).

Ответ: 800; 800; 360; 730; 840; 780; 80; 40.