Question 990036
<pre>
Let her average speed by r mph.

After 3 hours, since d=rt, she was r&#8729;3 or 3r miles down the road 
when Sam left.

So the distance between them when Sam left was 3r.

His catch-up rate was 43 mph to catch up the 3r distance between them,
so since d=rt, 3r = 43&#8729;2
               3r = 86
                r = 86/3 = 28 2/3 mph

Edwin</pre>