I’ve been out of school for a while, any recommendations on how to get back into the groove of math?

I graduated high school about 5 years ago. Functions and calculus were some of my best marks throughout high school (high 90s).

I have recently decided I want to go to university so I’ve applied to some mathematics and physics programs.

However, lurking around some math subreddits I’m reminded of how much stuff I’ve forgotten in the past 5 years.

Is there anyway through Khan to discover what I've forgotten and to quickly relearn it? I've heard about a Placement Test at Kahn but it seems they don't have it anymore? 

Thanks!