Question 1132154
Thirty minutes is half-hour.
<pre>
            SPEED         TIME        DISTANCE

As Done       x           600/x       600

If           x-5         600/(x-5)    600

Difference               1/2
</pre>

The starting equation is   {{{600/(x-5)-600/x=1/2}}}



STEPS:

{{{1200/(x-5)-1200/x=1}}}

{{{1200x-1200x+6000=x^2-5x}}}

{{{6000=x^2-5x}}}

Simplification should give  {{{highlight_green(x^2-5x-6000=0)}}}



Discriminant, {{{5^2+4*6000=24025=155^2}}}


{{{highlight_green(x=(5+155)/2)}}}

80 kilometers per hour