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

### Instruction:
 伊莉丝正在购买更多的狗粮。她买了一个15公斤的袋子，然后又买了一个10公斤的袋子，现在她有40公斤的狗粮。伊莉丝之前有多少公斤的狗粮？


### Response:
 两袋狗粮的重量是15 + 10 = 25公斤
伊莉丝之前已经有的狗粮总重量是40 - 25 = <<40-25=15>>15公斤