Answer:
17
Step-by-step explanation:
Let the two "middle" vertexes be x1 and x2, and let the "lower" vertex be y. We know that
[tex]1 + 5 + x1 = 1 + 5 + x2[/tex]
Therefore x1=x2. We'll call that value just x.
But now we have to be careful, because
[tex]5 + x + y = x + x + y[/tex]
Simplifying we can get the value of x:
[tex]x = 5[/tex]
Now, substituting back in, we get
[tex]1 + 5 + 5 = 5 + 5 + y \\ y = 1[/tex]
So, the sum of all vertexes is equal to
[tex]2 \times 1 + 3 \times 5 = 17[/tex]