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

### Instruction:
Tommy has 13 items in his pencil case. The pens are twice as many as the pencils and there's one eraser. How many pencils are there?

### 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.