Doing the maths ...

How much is that?

The owner of a golf course was confused about the gst on an invoice, so he decided to ask his secretary for some mathematical help.

He called her into his office and said, "You graduated from University and I need  some help. If I were to give you $20,000, minus 15%, how much would you take off?"

The secretary thought a moment, and then replied, "Everything but my ear rings."