can someone please help me find the answer to the following?

Using the Euler formula, we have:
F + V = E + 2 (F: faces, E:edges, V:vertices)
F + 12 = 18 + 2 (Replacing)
F + 12 = 20 (Adding)
F= 8 (Subtracting 12 from both sides of the equation)
The answer is 8.