ANSWER:
The carrying capacity (x) of the deer population is approx. 77.
EXPLANATION:
The carrying capacity is already marked on the graph - it's the horizontal line (although the line isn't straight). I think you basically just put a line through the middle of the maximum and minimum of that line to get the carrying capacity (approx. 77 or 78?).
I looked at a few similar graphs and that seems to be what they do but not 100% sure.
