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

### 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:
 ครึ่งหนึ่งของจำนวนหน้าของเซลีน่าคือ 400/2 = <<400/2=200>>200
หนังสือของแฮร์รี่มี 200 - 20 = <<200-20=180>>180 หน้า