1,X*(1-5%)=1900 X=2000
2,40*32%=X*2/5 X=32
3,X*(1+1/5)=24 X=20
4,v(圆柱)*(1+1/3)=60 V(圆柱)=45 V(圆锥)=15
7,4:X=8:9 X=4.5