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

### Instruction:
 Tommy ana vitu 13 katika kasha lake la penseli. Kalamu ni mara mbili ya penseli na kuna kiharusi kimoja. Kuna penseli ngapi?


### Response:
 Hesabu idadi ya jumla ya kalamu na penseli. Kuna vitu 13 - 1 kiharusi = <<13-1=12>>12 kalamu na penseli.
Kuna vitu 12 / 3 = <<12/3=4>>4 penseli.