Thank you all so much for the help so far, I know some of my questions were redundant and I apologize.

In the question they ask for f(x) and g(x).

The answers for both are; $\displaystyle f(x) = 2 \sqrt{x+4}$ & $\displaystyle g(x) = \frac {36-x}{3} + \sqrt {x+4} $

Leaving g(x) alone, I don't understand how they got the 2 in the f(x)... My formula doesn't have that.

PS; Thanks AllanCuz for the detailed solution to finding it w/r to y, which is what I'll have to do for the 2nd part but for now I need to use the original method with x.