Answer:
7 1/2 hours I believe is the correct answer. Hope it works!
If 30% of his collection is 12 cars, then we can use the fraction
30/12=100/x
x=40
I would say that
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1.7070004089
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is the only eighth root of 72.089.
72.089^(1/8) =
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1.7070004089
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