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

### Instruction:
Oscar wants to train for a marathon. He plans to add 2/3 of a mile each week until he reaches a 20-mile run. How many weeks before the marathon should he start training if he has already run 2 miles?

### Response:
 Oscar anahitaji kuongeza muda wake wa kukimbia kutoka maili 20 - 2 = <<20-2=18>>18.
Oscar atahitaji jumla ya wiki 18 / ( 2 / 3 ) = <<18/(2/3)=27>>27 kujiandaa.