The other dollar is in the pocket of one of the guys, because the other two have the other $2. Each guy paid $9 for the room, which is $27. Add in the $1 each they initially paid is the $30. Conversely, each guy paid $9 for the room, which is $27. Subtract the $2 the boy stole and you get the $25 room fee. The real riddle here is why three grown men need a single cheap motel room...