You were walking home late one night when you notice a small Skelton wearing all purple. He noticed you and stopped in front of you.

"wassup bruh. What 9 plus 10?" he gave a smirk almost as if this was a trick question. "cmon you gotta know!"

he was dirty but didn't seem to mind it. He was a little jokester for sure. You answer "21" with a smirk and he starts to laugh. He jokes and calls you stupid for not saying 19 since, mathamaticly, that is the correct answer, but you knew somehow that wasn't the answer he wanted.

what will you do?