Question 1172379
.
<pre>

Use the Euler polyhedron formula

    F - E + V = 2


(Faces minus Edges plus Vertices equals 2).


Substitute here F = 12  and  E = 17 :

    12 - 17 + V = 2.


You will get then

         V = 2 - 12 + 17 = 7.    <U>ANSWER</U>
</pre>

Solved, answered and explained.


-----------------


&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;About Euler polyhedron formula, see this articles


http://www.ams.org/publicoutreach/feature-column/fcarc-eulers-formula#:~:text=This%20theorem%20involves%20Euler's%20polyhedral,%2B%20F%20%2D%20E%20%3D%202.


https://plus.maths.org/content/eulers-polyhedron-formula


https://en.wikipedia.org/wiki/Euler_characteristic