I am so sorry I would love to help you but I haven't gotten that far in my classes, how long do you have? My sister should be coming home soon and she's learned this before
The 100 degree angle is supplementary to angle CED. This means CED will end up being 80 degrees. Since the angles in all triangles equate to 180 degrees 80 + 60 + angle D must equal 180 degrees. Therefore, angle D has to be 40 degrees.
