This is a short 2-3 minute video on all the angles of a triangle add up to 180 degrees. Two example problems are given to show the students how to find a missing angle if two are given.
I've geared this toward 5th grade math - the geometry standard, but it will probably be helpful for other grades.
This video is free. Hope it helps. Please check out my store for other things in 5th grade math common core. Thanks!