>>11924548don't make me sick. Khan academy is utter trash. even if you don't know a single thing about mathematics, start with counting from 0 to 100, then decimal representations (base 10), then teach them groups and adding of such groups, then division of groups by whole numbers (splitting in two, four, 3,etc.). Now you have all you need to learn from Lang's Basic Mathematics. I think the internet is an amazing resource but not for khan academy trash. I use it for libgen (pirating text books) and stackexchange and similar forums. As a rule of thumb, stay away from everything mainstream and popular with normies, it's almost always garbage dumbed-down trash and will hinder your understanding.
Once your kid has gotten through Lang then you can get him interesting in math by watching A Beautiful Mind or something idk (for me motivation comes from these movies and some podcasts on youtube like Lex Fridman). Then once he is motivated he can be introduced to functions, piecewise functions, domains, ranges, etc. In my opinion, I think it would be beneficial to teach him calculus at 10 or something at the latest. It's just a set of tools which have easy physical intuition. If you want I would also teach him simple classical mechanics so he can test out his skills in real life simple problems. Anyway good luck
