For the polyhedron, use Euler's Formula to find the missing number.
faces: __
edges: 11
vertices: 8
Using Euler's Formula for polyhedra:
F + V - E = 2
Plugging in the given numbers:
F + 8 - 11 = 2
F - 3 = 2
F = 5
Therefore, the missing number of faces is 5.