Question

Use Euler’s Formula to find the number of vertices in a polyhedron with four triangular faces.

Answer 1

Euler formula:
$V-E+F=2$
Since $F=4$ then 
$V-E+4=2\\V-E=-2\\V=E-2$ and $E=8$ (check the figure)
So:
$V=8-4=4$ is the number of vertices.

Answer 2

Answer:

$V=4$

Step-by-step explanation:

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

Let

V----> the number of vertices

E------> the number of edges

F------> the number of faces

$V - E + F = 2$

In this problem we have

$F=4, E=6$

substitute in the formula and solve for V

$V-6+4 = 2$

$V-6+4 = 2$

$V=4$

see the attached figure to better understand the problem