I have quite a few adult readers using my book to refresh and re-learn basic calculus and mechanics. You might consider checking it out[1]. It's not free, but very affordable.
I am the same, relearning a lot of linear algebra. It's a great book and my choice, so far, for this process. It does jump around a bit in some places but I have found, if something is not explained I keep on reading and some time later he comes back to it. Highly recommended.
[1] https://www.amazon.com/dp/0992001005/noBSguide preview: https://minireference.com/static/excerpts/noBSguide_v5_previ...