Here it goes:
"A woman walks into a deli and buys two cans of soda: root beer and gingerale. When she pays for the sodas, the clerk givers her change and a receipt. She then proceeds to draw a small triangle on the bottom of the receipt as well as the following equation: 3*13 = 39. The clerk notices all of this, and says to the woman, "I notice that you're a firefighter." How did the clerk know this?"
Solutions anyone please?

Please don't publish problems in the Forums. A visit to FAQ will explain why and give you further information.