In fact, there is no such thing as "monism". The questioner is only conducive to people's directional thinking and leads readers into the misunderstanding of thinking along a road. The figure should be calculated as follows: 30 yuan, one person is refunded 1 yuan, that is, each person goes out of 9 yuan, 3 times 9=27, and 25 yuan is given the room fee, and the waiter deducts 2 yuan.