For online math learning, I usually recommend Khan Academy. But it’s good to find other resources too. I recently came across Schoolyourself.org, a great site that could be helpful to you or your kids for math studies.
Using the site is free. You don’t even need to log in to access the lessons, though logging in allows you to record your progress. (I haven’t yet set up an account, but I think there are also more opportunities to review material if you’re logged in.)
From what I’ve seen so far, here’s what I like about this site:
– The videos are interactive. During each lesson, the video stops at various points, and you’re asked to solve problems. This means you can’t just listen passively. You need to be able to show that you’re paying attention and can figure out what’s going on.
– The lessons check that you have the relevant background knowledge. For example, at the start of the video on raising numbers to a negative power, you’re tested with a question on dividing exponents and given a chance to review if you’ve forgotten.
– Basic math doesn’t get overlooked. For instance, the algebra unit includes videos on arithmetic principles. This is helpful to students who are starting algebra but may have forgotten certain rules about multiplying negative numbers, for instance.
One drawback to the site is that it’s a little “calculator-heavy” in its approach. If you want to study how to multiply or divide decimals by hand, you may need to look somewhere else for a review.
But overall it’s a useful site that I recommend as a supplement to your math studies.
Bright Across the Lifespan 
Thanks for the info.! Always looking for more math resources. Not sure what kind of math you need, but you might want to check out my blog too. I have high school math videos and practice questions. Let me know what you think! 🙂
https://mathsux.org/