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

### Instruction:
 三脚龙有三条腿。在一群三脚龙中，总共有20个头和腿。这群三脚龙有多少只？


### Response:
 每只动物有1+3=<<1+3=4>>4个头和腿。
那么这群三脚龙有20/4=<<20/4=5>>5只。