By recommend, I mean content you actually find to be high quality, well done, and easy to absorb and follow. By relearn, I mean I have forgotten everything I ever learned in high school.
Kahn academy. It’s free and goes as deep as you want. I had to brush up on some stuff and it was great.
Helped me get through my engineering degree. Absolutely the best maths education I’ve ever seen.
As others said, Khan academy, but in the event that you need something even more broken down, patrickJMT on YouTube is a godsend.
I used Khan Academy when I reentered uni as a mature-age student and found it very helpful
If you graduate to college level you can try Opencourseware -> https://en.m.wikipedia.org/wiki/OpenCourseWare