Euler's theorem for polyhedra demonstrates the constant relationship
among the components of a given polyhedron: 
the number of polygons  +  the number of vertices 
=  the number of edges  +  2 
P  +  V 
=  E  +  2 

Take the cube for example: 

P = 6, V = 8, E = 12 P + V = 6 + 8 = 14 E + 2 = 12 + 2 = 14 
