This joke is a bit dated, but it still works.

A newly married couple was still getting their bearings down on the marriage. The wife had not yet figured out how to ask the husband for money. She felt a little skittish. She finally devised a strategy:

“Honey, I need to borrow ten dollars. But only give me five.”

“If you need ten, then why are you only asking for five?”

“Because that way I will owe you five and you will owe me five and we will be even.”