<PRE><B>Question 1013228</B>
Mario: 5 cars/3 hours=5/3 cars per hour
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Together: 7 cars /2 hours 
In 2 hours Mario details 2hrs(5/3 car/hr)=10/3 cars 
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7 cars-10/3 cars=21/3 cars-10/3 cars=11/3 cars
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When working together for 2 hours, Mario details 10/3 cars, leaving 11/3 cars for Julio.
Thus Julio: 11/3 cars/2 hours=11/6 cars per hour.
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For Julio to detail 12 cars:
12 cars /(11/6 cars/hr)=6.55 hours
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ANSWER: It would take Julio 6.55 hours to detail 12 cars.
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