Solve the math problem.
12 - 3 =
9
- 7
18 - 9 =
11
- 6
14
- 0
15
- 1
13 - 7 =
19
- 2
6 - 6 =
8 - 8 =
7 - 5 =
18
17 - 4 =
8 - 2 =
- 9
20
- 5
16
17 - 2 =
8
12 - 5 =
17 - 6 =
4 - 2 =