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

### Instruction:
There were 21 dollars in the cookie jar. Doris spent $6 from the cookie jar. Martha spent half as much as Doris. How much money, in dollars, was left in the cookie jar?

### Response:
 Martha alitumia 6/2=<<6/2=3>>3 dola.
Martha na Doris walitumia jumla ya 3+6=<<3+6=9>>9 dola.
Kulikuwa na dola 21-9=<<21-9=12>>12 zilizobaki katika kikombe cha biskuti.