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