1 =100*(20+2)=100*20+100*2=2000+200=2200
2 18*102=18*(100+2)=18*100+18*2=
398*31=(100-2)*31=100*31-2*31=
4 =(50+1)=50*9+1*9=
5 =(50-2)*7=50*7-2*7=350-14=336
1 =100*(20+2)=100*20+100*2=2000+200=2200
2 18*102=18*(100+2)=18*100+18*2=
398*31=(100-2)*31=100*31-2*31=
4 =(50+1)=50*9+1*9=
5 =(50-2)*7=50*7-2*7=350-14=336