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

### Instruction:
 约翰买了2打饼干。他吃了3个。他还剩下多少个饼干？


### Response:
 他买了2*12=<<2*12=24>>24个饼干。
所以他还剩下24-3=<<24-3=21>>21个饼干。