You have to split the isosceles acute triangle in the middle of the polygon down the middle, and find what the now right isosceles tringle is. Since we already know that there's a 50 degress and a 90 degress there all you have to do is add those two numbers together and subtract from 180. Thena after you've done that you just need to multiply 40 by 2 and bata bing, bata boom you have 80 degress as your top, you already have a 50 and the last one has to be 50. Divide 50 by 4 and you get 12.5
