Solve the following problem.
1. If a is indirectly proportional to b, then a=k/b, where k is a constant or fixed number. If a=8 when b=6, find the value of k.

Using the value of k in number 1, find:
2. a if b=3
3. a if b=4
4. a if b=12
5. a if b=1.5
6. a if b=3.6
7. a if b=4.8
8. b if a=3
9. b if a=4
10. b if a=4.5
11. b if a= 4.8
12. b if a=3.6
13. b if a=6