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

### Instruction:
 汤普森夫人买了3只鸡，每只3美元。她还买了一袋土豆。汤普森夫人总共支付了15美元。土豆的价格是多少？


### Response:
 3只鸡共计3美元 x 3只 = 9美元。
因此，土豆的价格是15美元 - 9美元 = 6美元。