( x - 80 ):40=640 , (x-80)×40=640 , x-80= 640:40, x-80= 640×40 4класс

1) (x-80):40=640x-80=640×40x-80=25600x=25600+80x=256802) (x-80)×40=64040x-3200=64040x=640+320040x=3840X=963) x-80=640:40x-80=96x=1764) x-80=640×40x-80=25600x=25680