This is really a �problem' with the way the situation is worded, not a problem of arithmetic. The three men paid 27 for the room, but only if you add in the 2 the bell boy kept. That 2 should be subtracted from - not added to - the 27, which gives the room cost of 25. Looked at another way, the desk-man has 25, the bell boy has 2 and the men have3, which equals 30, which is exactly where you started.