( x - 80 ):40=640 , (x-80)×40=640 , x-80= 640:40, x-80= 640×40 4класс
1) (x-80):40=640 x-80=640×40 x-80=25600 x=25600+80 x=25680 2) (x-80)×40=640 40x-3200=640 40x=640+3200 40x=3840 X=96 3) x-80=640:40 x-80=96 x=176 4) x-80=640×40 x-80=25600 x=25680