[KodiakLabs]

The simplest approach I think would be to start with Khan Academy. Well spoken clear and concise. You can go from a Highschool level towards subjects from first year university. Once there, it should be easier to self teach from books.

[hultner]

I can recommend this path, studied almost all my pre-engineering math this way 2011 and were better equipped for initial engineering courses then most of my peers. However it kinda capped out at high-school level (or atleast Swedish equivalents).

[KodiakLabs]

Interesting. Truth be told, I remember when it was simply him on YouTube. I guess to carry on, one would have to go for 3Blue1Brown to get the fundamentals of university math.

[ravenstine]

OpenStax textbooks(free and open source) are also good supplemental material.

[elbear]

I agree, because I'm on this path myself and have been for 200 days. I started by brushing up on my algebra and now I've reached integrals in AP Calculus AB.