Khan Academy is great. When I was taking AP calculus in highschool I failed to complete any homework and barely passed the class. But when it came time for the AP test I binged Khan Academy videos for 3 days beforehand and ended up getting a 5 (the max score). Great resource and even bingeable

Specifically these three courses [0][1][2] will take you from basic algebra to precalc. They're very thorough and I've found them extremely useful in upgrading my high school level math skills. I have heard that their calculus courses aren't sufficient though, and that it should be learned from somewhere else.

[0]https://www.khanacademy.org/math/math1 [1]https://www.khanacademy.org/math/math2 [2]https://www.khanacademy.org/math/math3