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

### Instruction:
 Selena读了一本有400页的书。Harry读了一本比Selena的书少20页的一半。Harry的书有多少页？


### Response:
 Selena的书的一半是400/2 = <<400/2=200>>200页。
因此，Harry的书有200 - 20 = <<200-20=180>>180页。