Honestly explaining base 15 first is probably the way to go, once you add symbols you can be like “ok now binary works the same way we just have to limit ourselves to two characters.”
I guess the way I’d explain it is take base 10 and replace all the digits with letters, then show how other bases are the same, you just have a different number of possible digits (however you choose to represent them - letters or actual 0-9 digits).
Honestly explaining base 15 first is probably the way to go, once you add symbols you can be like “ok now binary works the same way we just have to limit ourselves to two characters.”
I guess the way I’d explain it is take base 10 and replace all the digits with letters, then show how other bases are the same, you just have a different number of possible digits (however you choose to represent them - letters or actual 0-9 digits).