<PRE><B>Question 387876</B>
car will catch up to the bike when 
the distance for the car = distance for the bike
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distance =rate * time
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distance bike= head start distance + distance after car leaves
             = 12mph*3 hours + 12mph*t = 36+12t
distance car=30mph * t
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set distance bike=distance car
36+12t=30t
36=18t
36/18=2=t
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answer: the car will catch the bike in 2 hours after the cars leaves.</PRE>