(400-20)•2=400•2-20•2=800-40=760
(80-1)•5=80•5-1•5=400-5=395
(25-9)•4=25•4-9•4=100-36=64
(20-1)•7=20•7-1•7=140-7=133
(400-20)•2=400•2-20•2=800-40=760
(80-1)•5=80•5-1•5=400-5=395
(25-9)•4=25•4-9•4=100-36=64
(20-1)•7=20•7-1•7=140-7=133