The Hotel Problem

Problem
Liz, Pat and Anne check into a motel room that advertises a rate of $27 per night. They each give $10 to the porter, and ask her to bring back three dollar bills. The porter returns to the desk, where she learns that the room is actually only $25 per night. She gives $25 to the motel desk clerk, returns to the room, and gives the guests back each one dollar, deciding not to tell them about the actual rate. "Thus the porter has pocketed $2," Liz was calculating," while each guest has spent 10 - 1=$9, a total of 2+3x9=$29. What happened to the other dollar?

Solution
to be added...