Question

вычислите устно

 34x84-24x84

 45x40-40x25

 51x78-51x58

 63x7-7x33

Answer 1

1) 84(34-24)=840
2)40(45-25)=800
3)51(78-58)=1020
4)7(63-33)=210

Answer 2

34x84-24x84 = 84*(34-24)=84*10=840
45x40-40x25 = 40*(45-25)=40*20=800
51x78-51x58 =51*(78-58)=51*20=1020
63x7-7x33 = 7*(63-33)=7*30=210