Find the missing number: addition to 50

Every number is 50 or less.

1. □ + 8 = 10 What number goes in the box?
2. 1 + □ = 2 What number goes in the box?
3. □ + 3 = 7 What number goes in the box?
4. 4 + □ = 5 What number goes in the box?
5. 8 + □ = 12 What number goes in the box?
6. □ + 6 = 9 What number goes in the box?
7. □ + 7 = 13 What number goes in the box?
8. 9 + □ = 11 What number goes in the box?
9. 5 + □ = 9 What number goes in the box?
10. 18 + □ = 24 What number goes in the box?
11. □ + 6 = 22 What number goes in the box?
12. □ + 10 = 24 What number goes in the box?
13. 2 + □ = 6 What number goes in the box?
14. □ + 30 = 36 What number goes in the box?
15. □ + 13 = 36 What number goes in the box?
16. □ + 13 = 17 What number goes in the box?
17. □ + 32 = 34 What number goes in the box?
18. 10 + □ = 20 What number goes in the box?
19. 25 + □ = 32 What number goes in the box?
20. □ + 5 = 29 What number goes in the box?