Integral method:
Do not consider any intermediate process, do not consider other property that did not participate in any exchange. Before all contacts, see how much property Master Wang has; After the exchange, let's see how much property Master Wang has. The difference between the two lies in how much Master Wang lost.
Before all the exchanges, Master Wang's property was a pair of shoes, the value of which was 80 yuan (the purchase price of a pair of shoes was 40, and the purchase price of a pair of shoes was 80), real money and silver 100 yuan (for returning to neighbors in the future), and * * * was 180 yuan. After all the money has been exchanged, Master Wang lost his shoes, leaving 35 yuan's real money (change for customers) as 35 yuan. Total loss 180-35= 145 yuan.
Step by step:
Write down every step.
1. Master Wang gave shoes and got counterfeit money. At this point, Master Wang lost 80 yuan.
2. Master Wang gave the counterfeit money to his neighbor and got the real money 100 yuan. At this point, Master Wang earned 100-80 = 20 yuan.
3. Master Wang found the customer 65 yuan. At this point, Master Wang lost 65-20=45 yuan.
4. The neighbor asked Master Wang for 100 yuan, and Master Wang lost 100+45 = 145 yuan.
At this point, all of them have been exchanged, and Master Wang has lost 145 yuan.
Equivalent method:
Master Wang first gave the counterfeit money to his neighbor and got the real money 100 yuan. Later, I gave my neighbor 100 yuan in real money. All this is equivalent to no communication between Master Wang and his neighbors. Then what Master Wang lost was the shoes worth 80 yuan, and the 65 yuan change for the customer was 80+65= 145 yuan.
The results of the three methods are the same.
In fact, this kind of topic is still a bit difficult when it first came out. But more and more people succeeded. So the questioner began to play word games. For example, in this topic, the purchase price of shoes is a shoe 40 yuan, but the selling price is a pair of shoes 35 yuan. Discount is not that outrageous, is it? This is just a text trap, which makes people pay no attention.