Number analogies

9 is to 18 as 5 is to ___

5 is to 25 as 3 is to ___

3 is to 0 as 5 is to ___

6 is to 13 as 4 is to ___

5 is to 20 as 2 is to ___

11 is to 9 as 9 is to ___

16 is to 48 as 3 is to ___

12 is to 16 as 4 is to ___

10 is to 20 as 7 is to ___

7 is to 35 as 6 is to ___

8 is to 5 as 4 is to ___

12 is to 19 as 5 is to ___