12*(1/8+3/4-1/6)=12*(3/24+18/24-4/24)=12*17/24=17/245/埋橘运做[(5/2)/(1/15)]=45/[(5/2)*15]=3/(5/2)=6/56*7/12-1/弯悄团2=7/2-1/2=32+3x/4=23, 3x/4=21, x/4=7, x=283x+2/5*15=21, 3x+6=21, 3x=15, x=5x+0.4x=21, 1.4x=21, 7x=105, x=15