31.8*7.9=31.8*(8-0.1)=31.8*8-31.8*0.1=254.4-3.18=251.22
12.5*5.9=12.5*(6-0.1)=12.5*6-12.5*0.1=75-1.25=73.75
44.3*2.1=44.3*(2+0.1)=44.3*2+44.3*0.1=88.6+4.43=93.03

接下