The base of a pyramid has n sides write an expression for the number of faces of the pyramid

A pyramid always have a number of slant triangles equal to the number of the sides of the base.

This means that a pyramid always have the number of face which is one more than the number of sides of the base.

Therefore, given that a pyramid has n number of sides of the base, the expression for the number of faces of the pyramid is given by

number of faces = n + 1.