Description: Learn about the angles in a triangle and a little about exterior angles being the sum of the remote interior angles. Created by Sal Khan. Given the information over here, I want to figure out what the measure of this angle is right over there. And so you might want to give a go at it just knowing what you know about the sums of the measures of the angles inside of a triangle, and maybe a little bit of what you know about supplementary angles. This is a general way to think about a lot of these problems where they give you some angles and you have to figure out some other angles based on the sum of angles and a triangle equaling 180, or this one doesn't have parallel lines on it.*Teacher Advisor is 100% free.