1. 0 + 0 = 0 2. 1 + 1 = 2 3. 2 + 2 = 4 4. 3 + 3 = 6 5. 4 + 4 = 8 6. 5 + 5 = 10 7. 6 + 6 = 12 8. 7 + 7 = 14 9. 8 + 8 = 16 10. 9 + 9 = 18 11. 10 + 10 = 20 12. 11 + 11 = 22 13. 12 + 12 = 24 14. 13 + 13 = 26 15. 14 + 14 = 28 16. 15 + 15 = 30 17. 16 + 16 = 32 18. 17 + 17 = 34 19. 18 + 18 = 36 20. 19 + 19 =