70%x﹣4=80
x+40%x=2.1 =:15
x+50%=42 :x=:0.8
0.75:x=0.3:1.8 x-35%x=16
1+75%x=2.8 x:3=
7.2:x=
解:3.6x=57.6
3.6x÷3.6=57.6÷3.6
x=16