I have US H4 EAD. Can I take maths classes in my apartment. If so,is there any limit of children. Mine is a single bedroom apartment.
You have an unrestricted EAD, so you are authorized to do any kind of employment (including self-employment) in the US, as far as immigration is concerned. Of course, if you earn any income, make sure to report it on your taxes.
As for whether someone in general can teach children math in an apartment, that is a separate question. Perhaps your apartment lease has something that prohibits you from using it for a commercial purpose (not sure if this would count as a commercial purpose)? Or maybe there are restrictions on what you can do in your apartment from zoning laws in your city? Or the fire department has restrictions on how many people can be in your apartment? Maybe you should check if you need any license to be able to earn money teaching? I don't know about these kinds of things.