Question 1074383
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Let "r" be the speed at the first part of the trip, in km/h.
Then the speed at the second part is (r-7) km/h.


The "time" equation is 

{{{140/r + 63/(r-7)}}} = 3.


Solve it for "r". For it, multiply both sides of the equation by r*(r-7). You will get

140*(r-7) + 63r = 3r*(r-7).


Simplify and solve this quadratic equation.
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