195737

I created five quadrilaterals and calculated the angles by dividing them up into triangles. As I have already worked out all the angles in the triangles, I used that information to add up the angles in the quadrilaterals. I noticed that the opposite vertices in each quadrilateral all added up to 180 degrees and that it is common for 80 and 100 , and 60 and 120 to be the pairs of angles.