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