Three workers together can do a job in 12 days. Two of them work faster than the third worker. Each of the two faster workers works twice as fast as the third worker. How long will it take for one of the faster workers to do the job all by himself?

Let the third worker's rate be 1/x, so the two faster workers each have a rate of 2/x, giving a combined 1-day work of 5/x. Since the group finishes the job in 12 days, 5/x = 1/12, meaning x = 60 days for the third worker. One of the faster workers takes half that time, which is 30 days.

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