That’s tough, man. Practice with them. I worked as a project estimator/manager which required me to remember all of these formulas (which sometimes made little sense, hard to explain, etc). The more you use them, the better you get at it. You’ll find shortcuts, ways of remembering the various variables, etc. Just continue to use them either with problems or in a real world situations. Anything you can think of that can make you use them. Repetition is key. Keep at it, bite the bullet. You’re bound to find little idiosyncratic ways of remembering the tougher ones. Only advice I have, sorry. It’s awfully obvious, but it works.