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

### Instruction:
 Selena anasoma kitabu chenye kurasa 400. Harry anasoma kitabu chenye kurasa 20 chini ya nusu ya idadi ya kurasa za kitabu cha Selena. Kitabu cha Harry kina kurasa ngapi?


### Response:
 Nusu ya idadi ya kurasa za Selena ni 400/2 = <<400/2=200>>200.
20 chini ya nusu ya idadi ya kurasa za kitabu cha Selena ni 200 - 20 = 180.