① =
②0.25: =2:x
③ :3=x:4
④ : =x:0.1
⑤40: =x:1
⑥ =
①7.4﹣6.62+20.6﹣13.38
②×+×
③(-+)÷
④2×0.8×12.5×50%
⑤÷(÷+)
⑥×[1÷(+)]