Khan/khan-exercises — pull request #57318 by petercollingridge (2013-07-30 15:02:07+00:00)
Title: Adding and subtracting rational numbers

Four different exercises types for the first part of https://trello.com/c/EqP0nOuH/164-four-operations-with-rational-numbers.

I would appreciate feedback on how the hints could be improved.