Food Court Number Theory
I recently met some friends for dinner in an open-air food court underneath the New York City Highline. Much to my surprise, some arithmetic greeted us at the door.
Since beverages could not be purchased in cash, you first had to purchase beverage-vouchers which could then be exchanged for beverages. The beverage-vouchers only came in two denominations: $1 and $7.
I guess the food-court operators figured that most of their customers wouldn’t be comfortable solving stamp problems, so they were kind enough to provide some example solutions to common beverage equations.