2.3+5.7=
12.2﹣0.5=
140×0.3=
401﹣198=
3600÷12=
+ =
﹣ =
×240=
÷ =
25%×5.6÷ =
①4+0.7x=102
②x﹣+6=16
③x:12.5=8:
④x﹣x=18