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

### Instruction:
 动物园的爬行动物馆比热带雨林展区的动物数量少5只，如果爬行动物馆有16只动物，热带雨林展区有多少只动物？


### Response:
 设热带雨林展区的动物数量为x
3x-5=16
3x=21
x=<<7=7>>7