This should be a meaningful joke, right? The math teacher asked what was after 69? I should say count, after 69, it will be 70.
As I said just now, this is a joke with connotation, so I can't say more, because it's too detailed to be afraid of the title. You can know the meaning of "69 style" by yourself, and you will know why you gargle after 69 when you know the meaning.