Question 1173897
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Let x = the rate of the car, in miles per hour.

Then the rate of the plane is 3x miler per hour.



The time equation is


    {{{170/x}}} + {{{645/(3x)}}} = 7 hours,

or

    {{{170/x}}} + {{{215/x}}} = 7,


    {{{385/x}}} = 7,


    x = {{{385/7}}} = 55.


<U>ANSWER</U>.  The car rate was 55 miles per hour.
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Solved.