Answer:
c = P - a - b
Explanation:
We are basically trying to get "c" by itself. If we ask ourselves what is with the "c" that we need to get rid of in order to have "c" by itself, we have a positive "a" and a "plus 5". To get rid of the positive "a" we subtract "a" from both sides. That leaves
P - a = 5 + c
To get rid of the "plus 5" we subtract 5 from both sides. That leaves
P - a - 5 = c