Question 1107629
Fifteen minutes is the same as one-fourth of an hour.
<pre>
                   SPEED       TIME       DISTANCE
AtoB               12          d/12         d
BtoA               18          d/18         d
DIFFERENCE                    {{{1/4}}}
</pre>


Question asks for d, and it is found in solving {{{d/12-d/18=1/4}}}.