Answer:
c = -18
Explanation:
We need to distribute the -3 to each term within the parentheses. This essentially means finding the sum of the product of -3 with each of those inner terms:
-3 * c + (-3) * 14 + 3 = 15
-3c - 42 + 3 = 15
-3c = 15 + 42 - 3 = 54
c = 54/(-3) = -18
c = -18