Rob has some baseball cards, and a few are doubles. One third of Rob's cards are doubles, and Jess has 5 times as many doubles as Rob. If Jess has 40 doubles baseball cards, how many baseball cards does Rob have? Let's answer step by step:

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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Rob has 40 / 5 = 8 doubles baseball cards. Rob has 8 * 3 = 24 baseball cards. The answer: 24.