Below is an instruction that describes a task. Write a response that appropriately completes the request in Chinese. Please answer in Chinese.

### Instruction:
 斯奈德夫人过去的月收入的40%用于支付房租和水电费。她的工资最近增加了600美元，所以现在她的房租和水电费只占月收入的25%。她以前的月收入是多少？


### Response:
 假设她以前的月收入为p
房租和水电费的费用是p的40%，即(40/100)*p = 2p/5
她现在的收入是600+p
房租和水电费现在占月收入的25%，即(25/100)*(600+p) = (600+p)/4
将房租和水电费的两个表达式相等：2p/5 = (600+p)/4
两边乘以20得到8p = 5p + 3000
两边减去5p得到：3p = 3000
两边除以3得到 p = 1000