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

### Instruction:
Nico borrows 3 books from the library on Monday.  On Monday, he reads the first book with a total of 20 pages.  On Tuesday, he reads the second book with a total of 12 pages.  On Wednesday, he reads the third book.  If he has read a total of 51 pages from Monday to Wednesday, how many pages did he read on Wednesday?

### Response:
 เขาอ่านหนังสือ 20 หน้าในวันจันทร์ 12 หน้าในวันอังคาร และ 51-20-12=19 หน้าในวันพุธ