Triangle Sum Theorem! – It’s really easy! 
Triangle sum theorem is when all the sides of a triangle add up to
be 180 degrees.
For extra help, please watch the following video online.
http://www.phschool.com/atschool/academy123/english/acade
my123_content/wl-book-demo/ph-383s.html
Then complete Skills Practice p. 725-726 #1-6 (do not tear out)