x:3.6=20:0.9
(1-25%)=36 -=15 25% +×21=20
2x+30%x=13.8 13:x=6.5:4
:x=: 2:=3.6:x 12-4x=2.4
①11+2x=12
②0.7x+3.6x=43
③7:x=:
④