Hey, in case you're still looking, I think they would accept any classes you would offer here: https://www.zeqr.com/ Afaik, they accept classes in all areas and pricing and schedule is completely up to you, so that's cool :) Best of luck.
I've done English tutoring, but I would suggest a similar tactic that I've used: apply to as many platforms as you can find open for you and see which one works out best :)
One that I can remember of the top of my head that would definitely accept your classes is https://www.zeqr.com/ They're also fairly new, so they might even promote your classes themselves as a bonus, that's what I was offered recently.
Lynda.com would probably be a nice source of income, but yeah, I can imagine that the number of people trying to join them as contributors is very high :/
Good luck, mate!
Here's another platform for tutoring - https://www.zeqr.com/ They've got built-in video and audio calling and screen sharing, pricing and schedule is completely up to you and they accept all classes, I think I've already seen one or two Spanish classes listed. Best of luck!
One way to get an idea is to check what math tutors of various levels charge on Zeqr.
High school/college level tutoring is in the $20-30 range but I see people charging more when the subject gets specific. Anyway, I guess you'd charge thereabouts for elementary school as well.
You could use an online platform to make yourself available without geographic limitations, while still dedicating 1-on-1 attention to those who need math tutoring. Zeqr can help you with that. Technically it's for people who want to charge for their tutoring services, but nothing is stopping you from setting your price at $0.