1. 1a. 1b.
10 2
12 3
+ +
9 2
10 9
= =

2. 2a. 2b.
3 4
7 6
+ +
2 7
8 9
= =

3. 3a.
3b.
4
6 6
7
+
+
4
11 2
12
=
=

4. 4a. 4b.
1 8
7 9
+ +
3 1
7 5
= =

5. 5a. 5b.
3 5
10 11
+ +
2 6
8 11
= =

6. 6a. 6b.
6 2
9 7
+ +
1 8
4 11
= =

7. 1a. 1b.
7 8
9 10
− −
2 4
12 8
= =

8. 2a. 2b.
7 9
10 11
− −
1 3
10 12
= =

9. 3a. 3b.
3 5
10 12
− −
3 1
10 12
= =

10. 5a. 5b.
6 7
8 10
− −
1 4
5 6
= =

11. 6a. 6b.
5 2
9 4
− −
1 4
8 8
= =