B: Oh, that's impossible. I haven't a clue about skating, and anyway, I don't have any skates.
A: It's easy, you can get some there. And I'll be happy to show you _____.
We know the answer must be "how".
However, whether there's a rule that "how, why, and what" cannot be used individually? For example, we must use "how" in this way, "He doesn't know how to swim."
Hence, is it correct that we use "how" at the end of the sentence without adding the form of "to + verb".