How can you find the area of a polygon that is not one for which your know an area formula? i dont get it at all some one me

"Break into triangles, then add. In the figure on the right, the polygon can be broken up into triangles by drawing all the diagonals from one of the vertices. If you knowenough sides and angles to find the area of each, then you can simply add them up to find the total." -www.mathopenref.com/polygonirregulararea.html

By adding all the sides of the polygon and then divide of the sides.

2.4+3.2t. you get the answer by adding the ones with variables and ones without