Sorry I have to ask such a simple question, my brain is fried after today.
After substituting with a system of equation, I end up with this "simple" logarithmic problem.
$$5 - \log_2 (x - 3) = \log_2(x+1)$$
What property of logs am I looking for to solve this? I know the solution is $x = 7$. Properties of logs looks like it might be my downfall tonight.