The number of faces in a prism is two-thirds the number of vertices. What is the number of edges of the prism?

let the number of vertices be x.

number of faces = 2/3 x

let number of edges be y.

since F+V - E = 2

2/3x + x - y = 2

5/3 x - 2 = y..........(1)

therefore x is multiple of 3.

if x = 3 number of faces = 2 which is not possible.

if x = 6, number of faces = 4, number of edges = 8

the above equation is true for  x =12

number of vertices = 12

number of faces = 2/3 *12 = 8

number of edges = 20 - 2 =18

which is a hexagonal prism.

hope this helps you.