7/8-5/12+1/6=7/8-（5/12-1/6）=7/8+1/12=21/24+2/24=23/245/7*16.31-2.31/(7/5)=5/7(16.31-2.31)=5/7*14=1035/(7/8)*(1-2/7)=35/(35/56)=563.2x-3*4=52 x=40/3.2= 40*5/16=25/2v=πr^2h=3.14*9*12=339=340 合格...请问第三和第四小题能更准确一些么？35/[(7/8)*(1-2/7)]=35/(7/8*5/7)=35/(35/56)=563.2x-3*4=523.2x-12=523.2x=64x=20上面算错了= =