Respuesta :

carlosego
Euler's formula is given by:
 C + V = A + 2
 Where,
 C: number of faces
 V: number of vertices
 A: number of edges.
 Clearing A we have:
 A = C + V-2
 Substituting values:
 A = 21 + 14-2
 A = 33
 Answer:
 the missing number is:
 C.33