207×20= 1849÷719= 911+12=
40×(180+500)= 1÷86.5%= 8÷8÷28=
68×18﹣68= (23﹣14)×520= 25×49×4=
①x: =18:0.2
② =
③1.2:x=5:1.5
④4:9=x:3.6
⑤ =
⑥ : =x: