Question 1186015
.
<pre>

The "time" equation is


    {{{100/r}}} + {{{135/(r-5)}}} = 5  hours.    (1)


The solution can be easily guessed MENTALLY:  r = 50 km/h.


<U>CHECK</U>.  {{{100/50}}} + {{{135/45}}} = 2 + 3 = 5 hours.    ! Correct !
</pre>

Solved.


-------------


Alternatively, &nbsp;you can reduce equation &nbsp;(1) &nbsp;to the standard quadratic equation form

and solve it formally &nbsp;EITHER &nbsp;using the quadratic formula &nbsp;OR &nbsp;by factoring.



/////////////////



Keep in mind that &nbsp;the setup equation is written &nbsp;INCORRECTLY &nbsp;in the post by &nbsp;@josgarithmetic.


For your safety, &nbsp;IGNORE &nbsp;his post.