1, the customer "bought" one kilogram, and the purchase price of one kilogram of fish was 46 yuan: loss 46 yuan.

2.35 yuan a catty was on sale, and the customer bought a catty. The change is: 100-35*2=30 yuan.

So Master Wang lost 46+30=76 yuan.

Explain in detail:

1, suppose Master Wang has only 100 RMB on him, and only sells a catty of fish. 46 yuan for a kilo of fish. So when Master Wang came, his total assets were 100+46= 146 yuan.

2, 35 Jin Yuan, the customer bought one kilogram, and the selling price of one kilogram of fish was 35*2=70 yuan.

3. Gave Master Wang fake money 100 yuan. Master Wang had no change, so he asked his neighbor to change it 100 yuan. Master Wang gives customers change. 100-70=30 yuan. I gave it to 30 yuan, the client, and kept 70 yuan for myself.

At this point:

The customer took a catty of fish +30 yuan.

Master Wang has 100 yuan (originally brought), and 70 yuan has small change. The total is 170 yuan.

Neighbor counterfeit money 100 yuan.

4. When the money was found to be fake and confiscated by the bank, Master Wang lost his first 100 yuan to his neighbor, and at this time Master Wang only had 70 yuan's change.

When the master came, the total assets were 100+46= 146 yuan, and now 70 yuan is left.

146-70=76 yuan, loss of 76 yuan.