Khan/khan-exercises — pull request #54185 by petercollingridge (2013-07-16 15:49:51+00:00)
Title: Multiplying and dividing rational expressions

Multiplying and dividing expressions where each expression is in the form A / (Bx + C) or Ax / (Bx + C) or the inverse.
For example: 5x / (25x + 45) ÷ 7 / (40x + 72)

Solving requires cancelling a common expression of the form Ax + C