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
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?