Sihai network

Test your IQ from the missing ten Wen

Three scholars went to the exam and stayed in a hotel one day. The room price is 300 Wen per room. Three people share a room, and each person pays 100 Wen to the shopkeeper. Later, when the boss saw that the three were pitifully given a 50 Wen discount, he asked the bartender to take it back to three people. The bartender thought how to divide the 50 Wen among three people. It was better to take 20 Wen and return the remaining 30 Wen to three scholars.

The problem came out: each scholar actually paid 90 Wen, a total of 270 Wen. Add in the 20 Wen that the shopkeeper embezzles, and that's 290 Wen. Where is 10 Wen left?

See if you got it right?