Number of sides minus 2 equals the number of triangles within the polygon.
3 triangles
Three triangles
4
5 triangles.
5
6
A regular hexagon can be divided into 6 equilateral triangles by drawing diagonals between opposite vertices, if that helps.
You Can Get 6 triangles
There are 8
depends on what shape that vertex is in
21
If you are merely drawing from one vertex to all the others, the number of triangles in any n-sided figure is equal to n-2. In this case, a heptagon has seven sides, and thus (7 - 2) = 5 triangles can be drawn.