Explain simply why 10 is the correct answer to: Nancy earns $28 for working 4 hours. How many hours does she have to work to earn $70?. Explanation:

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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Nancy earns $28 / 4 = $7 per hour. Therefore, she has to work $70 / $7 = 10 hours to earn $70.