a,17.85+15+17-120
= 17 . (85 + 15) - 120
= 1700 - 120
= 1580
b,37.24+37.76+63.79+21.63
=37.(24+76)+63.(79+21)
=37.100+63.100
=100.(37+63)
=100.100 =10000
a,17.85+15+17-120 =1445+15-17-120=1323
b,37.24+37.76+63.79+21.63=37(24+76) + 63(79+21)=37.100+63.100=100(37+63)=100.100=10000
c,69.113-27.69+69.14+31=69(113-27+14)+31=69.100+31=6900+31=6931
@Huyền
c) 69.113 - 27.69 + 69.14 + 31
= 69.(113 - 27 + 14) +31
= 69.100 + 31
= 6931