Identify the number before and after a given two-digit number

1. 1 less, 1 more than 15
2. 1 less, 1 more than 17
3. 1 less, 1 more than 20
4. 1 less, 1 more than 8
5. 1 less, 1 more than 12
6. 1 less, 1 more than 37
7. 1 less, 1 more than 45
8. What Comes Next? - first even number after 13
9. What Comes Next? - first odd number after 13
10. What Comes Next? - first odd number after 12