（5x*0.85+9(66-x)*0.8）/(5x+9(66-x))=1-0.18
（4.25x+7.2*(66-x)）/(5x+9(66-x))=0.82
4.25x+7.2*(66-x)=(5x+9(66-x))*0.82
4.25x+7.2*(66-x)=4.1x+7.38(66-x)
4.25x-4.1x=7.38(66-x)-7.2*(66-x)
0.15x=0.18(66-x)
0.15x=11.88-0.18x
0.15x+0.18x=11.88
0.33x=11.88
x=36