Answer:
f(g(-3)) = 3
Explanation:
f(g(-3)) means that you have to solve for g(-3) and then solve for f(x) with the solution from g(-3)
g(x) = -x - 3
g(-3) = -(-3) - 3
g(-3) = 3 - 3
g(-3) = 0
Plug this into f(x).
f(x) = -x² - 6x + 3
f(0) = -(0)² - 6(0) + 3
f(0) = 3
f(g(-3)) = 3