Yes, I heard about Math Academy, and will likely give it a try at some point. The price tag has made me a bit reluctant, but given the near-universal praise, I might bite the bullet.
You could also try beast academy and aops. We are huge huge huge (did I mention huge?) huge fans of them and have worked through pretty much all of their classes (1st grade through pre-calculus thus far).
Beast academy is around 15/20 a month and apps is more but you can just buy the book and work through it. Richard (the aops co/founder) has a ton of YouTube videos as well.
A third option is aops’s alcumus - which is a free math problem database. We use that a bunch as well and you could use it to figure out what you know and don’t know
Reposting some advice I gave to someone on HN a few weeks ago:
Here's some advice I've been given by maths professors that I've put into practise. This stuff really works.
-- Make sure you can do it cold, as in make sure you can do things without looking at notes, or looking at wherever you learned it from. For example, say I give you a calculus problem, you should be able to solve it without any outside help, just you, some paper and a pen. No notes, no Google, nothing else. If you can't, then you need to study more and do more problems.
-- Build a routine. Make sure you study whatever it is you want to study every day at the same time and you'll find yourself wanting to do it after a habit is built. And if you miss a session, for whatever reason, you'll feel quite bad about it, and want to try extra hard in the next session because you know you're "behind schedule".
-- Actively recall whatever you've learnt. You can do this by quizzing yourself (make your own problem sets, or do problem sets made by others), and by using flashcards/anki for the things you have trouble memorising. This is one of the best ways to retain info.
-- Don't stress or get angry. You'll just stop the learning process. If you find yourself stressed, or angry, take a break. Remain calm, happy and curious.
What changed for me vs school days is that I don't have long blocks of time to work on a problem, so a tricky problem is likely to be skipped. I had to actively force myself to not skip hard things, meaning some days all I did was spend 10 minutes on the problem, find the wrong answer, and go to bed to try again tomorrow. Eventually I get em and move on much happier.
Unlike school days you have years to do this right.
OP, I recommend you take parent's latter points to heart. I (and likely you) need to re-learn how to learn in this phase of our lives, vs what we were used to as younguns whose entire job was just learn.
Thank you for your thoughtful reply! This sounds like exactly the situation that I am in: some knowledge, but full of holes. Starting from the very basics to build confidence seems like the way to go.
