(40-20)*2= 400*2 - 20*2=800-40= 760
(25-9)*4= 25*4 - 9*4= 100-36= 64
(80-1)*5= 80*5 - 1*5 = 400- 5= 395
(20-1)*7 = 20*7 - 1*7 = 140-7 = 133
400•2-20•2=760
25•4-9•4=66
80•5-1•5=395
20•7-1•7=133
(40-20)*2= 400*2 - 20*2=800-40= 760
(25-9)*4= 25*4 - 9*4= 100-36= 64
(80-1)*5= 80*5 - 1*5 = 400- 5= 395
(20-1)*7 = 20*7 - 1*7 = 140-7 = 133
400•2-20•2=760
25•4-9•4=66
80•5-1•5=395
20•7-1•7=133