If a polyhedron has 18 edges, 12 vertices, then it has ___ faces.
10
9
8
6
E = 18, V = 12, F = ?
Euler's Formula:
F + V - E = 2
F + 12 - 18 = 2
F - 6 = 2
F = 8
If a polyhedron has 15 vertices and 20 edges, then it has ___ faces.