There are many free textbooks online (1, 2, 3...), so maybe choose math, download something that starts simple, read it, if it is too complicated put it away and download something else. Download the textbooks to a book reader, so you can read them while you travel, etc. If you get stuck somewhere, search the answer online, if that fails ask in Less Wrong shortform.
You lost some time, but it is not too late to learn. If you start now, after ten years you will be happy that you did.
I used to be good at math at high school, but then I chose computer science at university, and ended up making stupid websites for 20 years. A few months ago, I decided to give it another try, and downloaded a few books. (I think I still have solid high-school knowledge, so I decided to go ahead and chose set theory.) First time I read a book, I didn’t understand most of it. Then I read it again and did some of the exercises, and suddenly it made much more sense. Now I understand even some Wikipedia articles which are definitely not written for beginners. (The intersection between “understands an esoteric topic”, “can explain it clearly”, and “willing to edit Wikipedia articles” is small, sometimes nonexistent.) I don’t have much free time with job and kids, but I try to regularly find an hour or two. But I am also picky; if a book doesn’t work for me, I throw it away and take another. That’s the advantage of free downloading. (Ahem.)
So, what now?
There are many free textbooks online (1, 2, 3...), so maybe choose math, download something that starts simple, read it, if it is too complicated put it away and download something else. Download the textbooks to a book reader, so you can read them while you travel, etc. If you get stuck somewhere, search the answer online, if that fails ask in Less Wrong shortform.
You lost some time, but it is not too late to learn. If you start now, after ten years you will be happy that you did.
I used to be good at math at high school, but then I chose computer science at university, and ended up making stupid websites for 20 years. A few months ago, I decided to give it another try, and downloaded a few books. (I think I still have solid high-school knowledge, so I decided to go ahead and chose set theory.) First time I read a book, I didn’t understand most of it. Then I read it again and did some of the exercises, and suddenly it made much more sense. Now I understand even some Wikipedia articles which are definitely not written for beginners. (The intersection between “understands an esoteric topic”, “can explain it clearly”, and “willing to edit Wikipedia articles” is small, sometimes nonexistent.) I don’t have much free time with job and kids, but I try to regularly find an hour or two. But I am also picky; if a book doesn’t work for me, I throw it away and take another. That’s the advantage of free downloading. (Ahem.)
See also: The Best Textbooks on Every Subject