If you want to, or need to learn math, you can do it completely online. I did it, and in this article, I will outline how to do it yourself. I will assume you want to start learning from the beginning so from Algebra I all the way to Linear Algebra and Calculus.
The reason I decided to learn math online by myself, is that I wanted to get more into Deep Learning, and I realized I need math. So, after trying out a lot of resources, I compiled a list of the best ones that I stumbled upon.
There are many good courses and videos on Prealgebra online, but the best one I found was Professor Leonard's Prealgebra Playlist. Professor Leonard is literally one of the best math professors I have ever seen. All of his playlists are amazing. The way he explains is unmatched. The only problem I found was that most of his classes were filmed for a University class and you have to go out and find exercises. This is not a big problem, but it can become tedious after a while. He also mentions which book the class is using, so you can just get the same book and learn alongside the class.
For Algebra, I would recommend Krista King's Become an Algebra Master course on Udemy. It contains thousands of exercises, really good explanations, and a certificate after finishing the course. Krista is really organized and explains concepts in a very clear way. Professor Leonard also has an Intermediate Algebra playlist, but I turned towards Krista's course because of the lack of exercises and solutions. Although, if you find some of Krista's explanations not sufficient, you can always go to Professor Leonard.
Since Professor Leonard still doesn't have a Linear Algebra course, I would have to recommend Krista King again. She has a course on Linear Algebra, that is also on Udemy. I haven't finished the course yet, but so far I am satisfied. Khan Academy also has a good Linear Algebra course, but I prefer the linear ;) and structured way of Krista's course.
For Calculus, I would go for Professor Leonard's class. You can find the whole playlist for Calculus 1 here. He also has Calculus 2 playlist, so you can just continue right away. I haven't done the Krista King course for Calculus, but I am sure it is great too, especially since it has those extra exercises.
So there you have it, a basic outline of how to learn math all by yourself. It is 100% doable, and it's fun at some point. I know I didn't include a lot of resources here, but I just wanted to give you smaller choice, so you don't end up having analysis paralysis. In a future post, I will give some resources to expand on Statistics, but since I haven't finished any course myself, I won't recommend anything for now.