87*五分之二+12除以二分之五+40% =87x0.4+12x0.4+0.4=(87+12+1)x0.4=100x0.4=40（一又七分之四+0.75+二又七分之三+ 一又四分之三）÷（3-一又三分支一）=(1又4/7+2又3/7+0.75+1.75)÷5/3=（4+2.5）x0.6=6.5x0.6=3.9...