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

### Instruction:
Selena reads a book with 400 pages. Harry reads a book with 20 fewer than half the number of pages Selena's book has. How many pages are in the book of Harry?

### Response:
Half the number of pages Selena's book has is 400/2=<<400/2=200>>200.
Harry's book has 200 - 20 = <<200-20=180>>180 pages.
#### 180