28×301%≈
1-=
425﹣199=
557÷69≈
5.2÷0.125÷8=
÷=
+=
8.2﹣2=
7-=
×0+3=
①x-x=2
②=6:x
①5.58-+5.42-
②64÷+37×40%﹣0.4
③÷[×(0.4÷)]