22﹣12=3 32﹣22=5 42﹣32=7
62﹣= ﹣992=
0.1×0.4= 16÷0.8= 720﹣180= 0.65+9.35=
:= ×0= ÷51= 0.01×99=
÷( + × ) 10.15﹣6.25﹣3.75+8.85
( + )×12+ 65÷ -38× +
①20%x﹣30=50
②42: =x:
③ =