The correct answer is 155 yuan.

The way to solve the problem is that 45 yuan bought a catty of fish, and the customer 35 yuan bought a catty. That is to say, Master Wang 35 yuan sold a catty of fish, and Master Wang lost 90 yuan first (a catty equals two catties). Then Master Wang asked 65 yuan for money, 90+65= 155, and Master Wang always lost 155. Or think about it from another angle: neighbors in three people don't make money or lose money. They just need to consider how much money they earned by buying fish, and that is the money that Master Wang lost. Buying fish means that 90 yuan starts with a kilo of fish, and 65 yuan starts with change, free of charge. In total, * * * earned 155 yuan, which means that Master Wang lost 155 yuan.