Question 1175717
.
<pre>

Let d be the distance between the cities.


Write the "time" equation


    {{{d/60}}} - {{{d/72}}} = {{{1/4}}}   of an hour   (which is 15 minutes)


To solve it, multiply both sides by 360 (LCM of numbers 60, 72 and 4).  You will get


    6d - 5d = 90

       d    = 90.


<U>ANSWER</U>.  The distance is 90 kilometers.


<U>CHECK</U>.   {{{90/60 - 90/72}}} = {{{540/360 - 450/360}}} = {{{90/360}}} = {{{1/4}}} of an hour.   ! Correct !
</pre>

Solved.