Question 1207746
<pre>
                    SPEED             TIME           DISTANCE

SLOWER              r                 d/r              d

FASTER             r+10              d/(r+10)          d

DIFFERENCE                            1/2
</pre>

Just seem easier to pick the unknown distance that each travels until each
arrives to be the variable.


{{{highlight_green(d/r-d/(r+10)=1/2)}}}


This analysis is better:
Both start at reference spot 8 a.m. 
Faster car completes distance in 3 hours (at 11 a.m.)
so slower car needed 3.5 hours (the half hour difference)
<pre>
                    SPEED             TIME           DISTANCE

SLOWER              r                 3.5              d

FASTER             r+10               3.0              d

DIFFERENCE                            1/2
</pre>
{{{highlight_green((r)(3.5)=(r+10)(3))}}}-------because both traveled the same distance.

{{{3.5r=3r+30}}}

{{{0.5r=30}}}

{{{highlight(r=60)}}}----------speed for slower car

{{{r+10=highlight(70)}}}--------speed for faster car