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Equation
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y = 8x + 10
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Given Information
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y = amount of time spent altogether
x = number of workout machines.
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Conclusion
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The slope, which is 8, is the amount of time he spent on one workout machine.
The y-intercept, which is 10, is a constant, independent from the time he spent on the machines. Therefore it is his warm up time.
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Answer : C
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