①x:15=4:5 ② ③ ④
×[-(-)] ×+÷
= 28%:6=x:25
1-x= = :x=3×
①3x-3.7=21.2 ② ③30%x+40×0.12=6
8:x=0.8:3
60%x+14=32.6
5(x-2.8)=140