Short version: Start at whatever math level you feel you can do confidently, grab that textbook, and work up from there. I highly recommend the Singapore method - there is a reason Singapore leads the world in math scores.

Long version: I actually never grasped math at all in school due to a combination of undiagnosed dyscalculia/bad math teaching in elementary and teachers who would get frustrated and do it for me on tests in middle/high school. I could memorize steps long enough to fake my way through a unit, but I had NO grasp of the actual material. (I did great in geometry because proofs required explaining why you get a result, not just “do these steps.”)

So in my 40s, crying over basic conversions on the amateur radio exam, I actually bought myself a set of elementary math textbooks and started from counting and number relationships (pairs of numbers that make 10 for example).

IT CHANGED MY LIFE. And algebra onward was easy because I finally learned to understand the relationships, not just memorize steps.

So yeah. Start with the math you know and look for books/materials that clarify how you get certain results and not just what steps to plug in. Make it interesting to you. Is my two cents.

As a high school librarian, I agree with CPS here. Google’s AI “search results” have imposed a new layer of difficulty in teaching research and critical thinking skills, while adding no benefit to those processes. I have several students who think LLM output must be accurate because it comes from an LLM, or that AI search summaries are a reliable source on their own - no need to click the included links to see if AI matches. The quality of student work suffers. I too would rather no Google than mandatory AI search.

I have been judged, and rightly so. For even the cats within reach of me receive no pets or treats. Woe unto me, a sinner

(I did penance after posting this i swear)