For this chain-of-thought reasoning and answer, what was the question?
Let x be the number of feet in John’s pool. 2 * x + 5 = 15. 2x = 10. x = 5.
 A: 5

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
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Q: John's pool is 5 feet deeper than 2 times Sarah’s pool. If John’s pool is 15 feet deep, how deep is Sarah’s pool?