14. (n-5)*4+7
15. No, this would not be neccesary because if I were to distribute 1/2 to both 4 and 6, I know that I would get half of those numbers which would give me 2x+3. I also know that if I distribute 1/3 to both 9 and 24, I would get 1/3 of each number which would be 3 and 8.
