khan academy is the best for ANY age. Start from basic algebra and progress through trig, geometry, calculus 1,2,3 and linear algebra, and you'll be fine. That'

khan academy is the best for ANY age. Start from basic algebra and progress through trig, geometry, calculus 1,2,3 and linear algebra, and you'll be fine. That's what I did. Should take a few months depending on work ethic