Question 1150145
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Before the catching moment, the minivan was on the way 7.5 hours, from 8:00 am to 3:30 pm.

                            The car     was on the way half an hour less, i.e. 7.5-0.5 = 7 hours.


Let x be the average speed of the minivan, in miles per hpur.

Then the average speed of the car was (x+5) mph, according to the condition.


To the catching moment, they covered the same distance.  Hence,


    7.5*x = 7*(x+5).


From this equation,


    7.5x = 7x + 35

    7.5x - 7x = 35

    0.5x      = 35

       x      = {{{35/0.5}}} = 70.


<U>ANSWER</U>.  The minivan average speed was 70 mph.  That of car was 70+5 = 75 mph.
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Solved.