Hey Ian,
Great question. We have a ton of students in your exact same position and although we start with the basics, the course does assume a command of fundamental math skills. To help students get prepared before their courses, we have a supplemental book called Foundations of GMAT Math which comes included with our course materials. If you have an account on our website, you also have access to a Basic Math Diagnostic which will let you know whether or not you should go through Foundations of Math. However, my personal recommendation is to take a look at Foundations of Math if you're even slightly concerned that you might need a refresher.
Hope this helps!
Matt
Matt Mapplebeck
Manhattan GMAT Representative
