None.
Vertices is a plural term and therefore "a vertices" cannot exist. As a result "a vertices" cannot have any vertices. In fact, it cannot have anything apart from non-existence.
it has 30 vertices
11 vertices
It has 12 vertices
A dodecagon has twelve vertices.
A polygon has as many vertices as it has sides and so in this case it will have 20 vertices.
A pentacontagon has 50 vertices (not vertices's!).
16 vertices.16 vertices.16 vertices.16 vertices.
8 vertices
Eight vertices
it has 30 vertices
5 vertices
11 vertices
8 vertices
There are 10 vertices.
4 vertices
8 vertices.
It has 8 vertices