Question 1140673
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Let x be the average speed of the slower car, in kilometers per hour.


Then the faster car's average speed is (x+3) km/h.


The "time" equation is


    {{{310/(x+3)}}} = {{{215/x}}}.      { " in the same amount of time " )


Solve it for x.


For it, cross multiply to get


    310*x = 215*(x+3)

    310x = 215x + 645

    310x - 215x = 645

    95x = 645

    x = {{{645/95}}} = 6.8 kilometers per hour (approximately).


Very strange answer, for the car' speed - but such are the input data in your post.
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