Answer :8.18 minutes
Explanation
GIVEN
• Adrian takes 15 minutes to run around the track = 1 /15
,
• Jeremy takes 18 minutes to run around the track = 1/18
CALCULATE WHEN THEY BOTH RUN TOGETHER :

This means that it will take them 90/11 minutes = 8.18 minutes for both boys to return at the starting point at the same time