So, long story short, I'm trying to teach myself some of the basics of linear algebra (if you want to know why, see the last paragraph). I found an awesome video series on Khan Academy that I'm going through to get started. However, there aren't any practice problems on the Khan Academy page.
Where could I find free, simple online problems to practice the stuff I'm learning in the videos? Requirements would be that it is somewhat simpler (I'm in 8th grade), online, and free. I wouldn't mind a textbook if it is, again, online and free. Specifically, right now I just finished a video about vector multiplication and addition.
As for why I'm trying to teach myself the basics of linear algebra in 8th grade, I'm trying to teach myself a bit about quantum computing, and I found a video series that will teach it (including the quantum mechanics behind it) but it requires some knowledge of linear algebra. So.