Law of Polygon of Forces:

If more than two forces are working on a body, then their resultant may be found by repeated applications of the parallelogram law or the triangle law. You can start with any two forces and determine their resultant primary and then add vector ally to this resultant the remaining forces taking one at a time. In the ultimate form of the repeated procedure, a polygon would be completed.

In other terms, if more than two coplanar forces meet at a specific point, their resultant can be found by the law of polygon of forces, that states that, "If a number of forces working at a point are such that they can be represented in magnitude and direction by the sides of an open polygon taken in order, after that their resultant is represented in magnitude and direction by the closing side of the polygon but taken in the opposite order".