Question

A polyhedron has 8 vertices and 14 edges. How many faces must it have?

Answer 1

We know that

The Euler's formula state that, the number of vertices, minus the number of edges, plus the number of faces, is equal to two

V - E + F = 2
clear F
F=2-V+E

in this problem
V=8
E=14
F=?
so
F=2-8+14
F=8

the answer is
8 faces