2.3+5.7=
12.2﹣0.5=
140×0.3=
401﹣198=
3600÷12=
+ =
﹣ =
×240=
÷ =
25%×5.6÷ =
( + )× +
( ﹣ + )÷
5× +14÷4﹣19×0.25
①4x÷ =6
②160%x+4.5×20%=8.9
③1.8:x=27:60