Question 1021535
The equation stating  600=55x+60y makes no sense.


RT=D is basic travel rates rule.  Assign variables and make a data table.


<pre>
                 rate            time           distance

UNCLE             60              y              60y

AUNT              55              x              55x

Totals                            10             580
</pre>


I assigned variables to times, but you assigned variables to distances.  This is simply a matter of choice of the person analyzing and solving the problem.   Either way is good.