Is there a difference between the 80th percentile and the top 80%?

Actually, yes there is. Being in the 80th percentile means that you are smart than 80% of the people (i.e. out of 100 people, you would be smarter than 80 of them). However being in the top 80% means that you are a part of the 80 smartest people out that same 100. 

Byou start by adding them all and setting them equal to 180 since that is half of the total degrees in a circle.(2x+8) + (3x-14) + (3x-14) = 1808x-20 = 1808x = 200x = 25