addition 1-5
1+1
what is 2
2-1
what is 1
6+6
what is 12
12-6
what is 6
2+2
what is 4
4-2
what is 2
7+7
what is 14
14-7
what is 7
3+3
what is 6
6-3
what is 3
8+8
what is 16
16-8
what is 8
4+4
what is 8
8-4
what is 4
9+9
what is 18
18-9
what is 9
5+5
what is 10
10-5
what is 5
10+10
what is 20
20-10
what is 10