Second: 270 yuan = the accommodation fee actually charged by the boss, 250 yuan+20 yuan who was greedy by the waiter himself.
In and out here are all equal, so naturally there is no conclusion 10 yuan.
The concept of "So a person takes out 90 yuan to stay in a hotel, 3×90=270, plus the greedy waiter 20 yuan, 270+20=290" is wrong! 20 is included in 270.