1. First, let the lengths of each side of the convex polygon be a, b, c, etc. The perimeter of a convex polygon is the sum of the lengths of all its sides.

2. Secondly, the perimeter p of a convex polygon can be expressed by a formula: P equals A plus B plus C.

3. Finally, this formula tells how to calculate the perimeter of a convex polygon, so the sum of the perimeters of this convex polygon is A plus B plus C.