Gil Strang's books are probably even better for an adult with little math background.

Intro to Linear Algebra: http://math.mit.edu/~gs/linearalgebra/

Strang does a GREAT job explaining the intuition behind linear algebra. The book is targeted at first-year undergrads and an adult with just high-school math could work through it.

Bonus: if you're interested in machine learning, you must learn linear algebra.

More advanced is this Strang masterpiece: Intro to Applied Mathematics. http://bookstore.siam.org/wc02/ It covers a lot of the applied math that we focused on pre-AI and pre-cloud computing. Diff eqs, diffusion equations, Fourier analysis, numerical methods, phase plane analysis, optimization, complex anlaysis.