Fill in the blanks with the correct number.

1. 4 + ___ = 1 + 8

2. 1 + ___ = 10 + 10

3. ___ + 1 = 1 + 2

4. 10 + 8 = ___ + 14

5. 7 + 2 = 9 + ___

6. 6 + 4 = 8 + ___

7. 4 + 4 = 7 + ___

8. 18 + 2 = 16 + ___

9. 13 + 3 = 15 + ___

10. 20 + 10 = 25 + ___

11. 16 + ___ = 10 + 7

12. 4 + ___ = 4 + 5

13. 8 + 1 = 7 + ___

14. 15 + 3 = 17 + ___

15. 9 + 10 = 16 + ___

16. 9 + 1 = 8 + ___