I do not know what the formula is for a triangle but I do know the formula for a rectangle which should help step (1) each corner has a number so think of corner 1 10 corner 2 25 corner 3 10 corner 4 26 this is just and example so u have all of your corners what you do first is you add all of the corners together then that's how you get your answer! Hope this helps! :)
