Question 854343
They meet the first time when the sum of their distances is the track perimeter.

Let t = time for first meet, hours


{{{15t+25t=400(1/1000)}}}  the extra factor is to put meters into kilometers.

{{{(15+25)t=0.4}}}
{{{t=0.4/(40)}}}
{{{t=4/400=highlight(1/100)}}} hours

{{{(1/100)*60}}} MINUTES
{{{3/5}}} minutes
{{{(3/5)minutes*60*second/minute=highlight(36*seconds)}}}