口算。
12-7= 8+9= 13-9=
50+2= 25+9=
3+20= 20+45=
84-60= 63-6= 18-9=
48+2= 79-40= 15-6=
7+8= 11-2=
37+50= 80-8= 23+8=
4+9= 13-7=
35+6= 70-30= 57-7= 2+70= 69-60=
89-9= 44-40= 14-7= 3+90= 16-8=
17-9= 12-6= 13-5= 27+9= 12-4=
11-4= 33+8= 42-7= 56-9= 8+49=
6+6= 28-8=
35-9= 42-6=
37+8=
94-7= 85-30= 53-9= 66-8= 50-7=