A triangle has three sides in total. If it has more than three sides, it is not a triangle. One of the three sides is called the 'base' ... usually the side that the triangle is resting on.
The base has three sides.
Five One base and four sides
An octagon is a plane figure. It has eight sides, but no real base.
A cone only has a base, no sides
4 sides
A ___ pyramid is a pyramid with ___ as its base. In this case, we have a nonagon, a nine-sided polygon, as the base. So, if you imagine each edge of the nonagon as having one triangular side coming off of it, and all of the triangular sides meeting at a point over the base, you then have 9 sides, one for each edge, plus the base itself - 10 sides total.
2 sides, the base and the cone.
5 sides
One side will be a square. It is the base. The lateral sides are triangles.
5... base and one triangle on each side
4 triangular sides and 1 square base