Ask HN: How to learn math from zero for adults?
For me "For dummies" series of math books works well: https://www.dummies.com/category/books/math-33720/
Start with "Basic Math & Pre-Algebra For Dummies" if you do not understand math at all. After get Algebra I and Algebra II. After Geometry, after Trigonometry after Precalculus or Directly Calculus.
I am now at Algebra II and going well with self-study.