It's kind of a big picture, sorry.
[Image: http://i57.photobucket.com/albums/g206/whyrainfalls/Triangles.png]
What the poop? Resize ftl. Hopefully you can still tell what I did even though you can't read it.
The words from top to bottom say,
In every Circle: (180-some amount)
Factor the unknown amounts, or the 180s depending on which way you want to look at it.
You know the sum of all the unknown amounts, the angles of a triangle, is 180.
Simplify.
(180-something)+(180-something else)+(180-another thing)=Answer
(180+180+180)-(All the somethings)=Answer
*All the somethings = 180
180+180+180-180 = 180+180 = 360