23-6=
45-9=
38+2=
50-8-20=
83-5=
81-70=
6+15=
48+20-7=
2+35=
40+59=
66-6=
18+(54-4)=
65+7=
57-7=
87-5=
93-(68-60)=
31+8= 20+39= 36-24= 65-35=
87
37
43
(个)