I don't know how many times I have explained this question.

Analysis: Master Wang bought a pair of shoes with 30 yuan, gave the customer a pair of shoes when he sold them, and returned 30 yuan to the customer because it was fake money.

It is equivalent to giving the customer 60 yuan, which means losing 60 yuan.

You may not understand that Master Wang still has 20 yuan. Let me explain it to you in detail.

Master Wang still has 50 yuan, neighbor, but Master Wang has it (neighbor's house is 50, customer is 30, and there is 20 left).

That is to say, as long as Master Wang Can adds 30 yuan money to his neighbor, he will pay him back 50 yuan money.

That is to say, Tim 30 yuan+sells a pair of shoes at a loss.

* * * 30+30=60 yuan.