I have quite a long holiday this year to myself, so I've decided to work on improving my math. So, could you please recommend some nice online courses to me.
Thanks in advance, and please keep in mind that I'm 13, so some basic Maths courses should do!
In my last few years of high school, I used MIT Open Courseware to study multivariable calculus, differential equations, and linear algebra. I was using them pretty seriously, i.e. I would print out the exams and give them to a teacher at the beginning of a semester and when I had done enough of the homework, they would proctor the exam for me. If that's not what you want then you can take this with a grain of salt.
Nevertheless, I felt like I learned pretty well from them, and I enjoyed it quite a bit. Of course, you shouldn't be hopping into a DEs course because that's only going to make you frustrated or quit, but they do have some courses and syllabi which at least seem like they are at a more basic level (although I stress more basic: these are all courses which were taught at one point to MIT students…).
Here are the four I can see, in order of how much I recommend:
My main advice would be this: No matter what service you use, it will be way easier to learn if there are videos. I was always the kid who just learned things from books in middle school and high school, but when I took those courses I really appreciated having somebody talking it through to me. Keep in mind I haven't actually taken these classes from MIT OCW, but from my college, so any or all of them may not be any good— but I would bet that at least one of them is.