Answer:
20
Explanation:
A dodecahedron is a three-dimensional figure made out of 12 regular pentagons. It resembles a soccer ball, just more rough on the edges.
So, it has 12 faces made out of regular pentagons. Each summit/vertex is a meeting point for 3 different pentagons.
So, you can easily calculate the number of vertices:
How many pentagon vertices in total?
12 pentagons with 5 vertices / pentagon = 60 vertices in total
But each vertex meets with two others... so you have to divide the number of total vertices by 3... so 60 / 3 = 20.