ExplanationIf Sue completed exactly one more lap than Rob, she ran 10 more miles than Rob. If Rob ran d miles, then Sue ran d + 10 miles. Rob and Sue began running at the same time, so they ran for the same amount of time. Let t represent the time they spent running. Fill out a chart for Rob and Sue, using the formula Distance = Rate × Time (D = RT):

| D(miles) | = | R(miles per hour) | \(\times\) | T (hours) |

Rob | d | = | 6 | \(\times\) | t |

Sue | d+10 | = | 8 | \(\times\) | t |

There are two equations:

\(d = 6t d + 10 = 8t\)

Substitute 6t for d in the second equation and then solve for t:

\(6t + 10 = 8t\)

\(10 = 2t\)

\(5 = t\)

Hence option C is correct!
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Sandy

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