To solve the equation, we need to isolate the variable c. First, we can combine like terms by adding c to both sides of the equation. This gives us -7 - 3c = 8. Next, we can simplify further by adding 7 to both sides, resulting in -3c = 15. To isolate c, we divide both sides of the equation by -3. This gives us c = -5. Therefore, the correct answer is c = -5.