How do you quickly solve this problem?

Test Preparation SAT Preparation
1

<p><a href="http://i.imgur.com/rVkit.jpg%5B/url%5D"&gt;http://i.imgur.com/rVkit.jpg&lt;/a&gt;&lt;/p>

2

<p>The figure the angles are in is a quadrilateral, so the sum of its interior angles is 360 degrees.</p>

<p>2a + 3b + c = 360
c = 360 - 2a - 3b, (E)</p>

3

<p>^Wow, I never saw that before. I just did it with triangle angle sums. Still got the right answer, but my way is slower and more mistake-prone.</p>

4

<p>WOW. I can’t believe I didn’t see that… I did it pi’s way too (I still ended up with an 800 on that practice test though). So much for USAMO lol.</p>