https://mathacademy.com/courses/mathematical-foundations-i https://mathacademy.com/courses/mathematical-foundations-ii https://mathacademy.com/courses/mathematical-foundations-iii
We also have courses on Linear Algebra and Mathematics for Machine Learning:
It's not free, but our adaptive, AI-driven algorithms makes it the most efficient way to learn math that you're going to find. We've had numerous students master 3-5 years of math in a single year.
We're still in beta and haven't done a proper Show HN yet, but we're getting there!
I'm the founder, so I'd be happy to answer any questions.
 website https://minireference.com/  PDF preview and sample chapter = https://minireference.com/static/excerpts/noBSmathphys_v5_pr...  concept map = https://minireference.com/static/conceptmaps/math_and_physic...
If you prefer something focussed on a review of high school math topic, then you might prefer the "green book" instead, see https://nobsmath.com/
And the books all have complete solutions manuals available so you can get immediate feedback.
You could use programs like Anki to schedule your review of defintions you've understood and problems you've solved to supercharge your learning as well.
I recommended a lot of people these courses and myself went over a few videos to revise Trigonometry.
I can vouch for the quality.
It assumes you have some algebra, but does not require college algebra.
it really takes you from the ground up all the way to advanced subjects. He published multiple books on various levels of mathematics.
The explanations are great and the examples and excises are such that you can just do them in your head.