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

### Instruction:
 曲奇罐里有21美元。多丽丝从曲奇罐里花了6美元。玛莎花了多丽丝的一半。曲奇罐里还剩下多少钱？


### Response:
 玛莎花了多丽丝的一半，所以玛莎花了6/2 = <<6/2=3>>3美元。
玛莎和多丽丝一共花了6+3 = <<6+3=9>>9美元。
曲奇罐里原本有21美元，所以现在还剩下21-9 = <<21-9=12>>12美元。