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

### Instruction:
Derek was 6 years old when he had three times as many dogs as cars. Ten years later, after selling some of his dogs and buying 210 more cars, the number of cars became twice the number of dogs. How many dogs does Derek have now if he had 90 dogs when he was six years old?

### Response:
 Ikiwa Derek alikuwa na mbwa mara tatu ya magari alipokuwa na miaka 6, alikuwa na magari 90/3 = 30.
Alipokuwa na miaka 6, Derek alikuwa na mbwa 90, ambayo inamaanisha alikuwa na mbwa 90 - 30 magari = 60 mbwa zaidi ya magari.
Baada ya miaka 10, Derek alinunua magari 210 zaidi, jumla ya magari 30+210 = 240.
Ikiwa idadi ya magari ni mara mbili ya idadi ya mbwa, Derek kwa sasa ana mbwa 240/2 = 120