Ответ:
\(980-80-100=800\); \(640-40+200=800\); \(290+70=360\); \(680+50=730\); \(140\cdot6=840\); \(260\cdot3=780\); \(480:6=80\); \(360:9=40\).
\(980-80-100=800\); \(640-40+200=800\); \(290+70=360\); \(680+50=730\); \(140\cdot6=840\); \(260\cdot3=780\); \(480:6=80\); \(360:9=40\).