Khan/khan-exercises — pull request #44584 by davemajor (2013-04-12 10:45:45+00:00)
Title: New exercise: Quadrilateral Angles 2

Really simple modification of Quadrilateral Angles in response to [Card #558](https://trello.com/c/9GhcGgYz).

Shows a range of quads with a single unknown angle for the learner to calculate.