Salmon Khan is a brilliant man with a knack for explaining key ideas on the SAT Math. In fact he goes through the entire range of math on the SAT. Don't believe me. Check it out by clicking here you will see what I mean. Scroll down and you will see a range of subjects that Mr. Khan talks about. If you don't understand, play the videos again. Mr. Khan provides clear, simple visuals.
You can even gain points if you log in using a GMAIL account. It appeals to those who like to gain points to show that you understand what Mr. Khan is showing you on the video. By the way, it is FREE. It is fun, user-friendly, online learning.