Answer: If they start running at the same time, then it will take 30 minutes until they complete a lap together.
Explanation:
Given: Stephanie can run one lap around a track in 5 minutes. Lisa can run one lap in 6 minutes.
If they start running at the same time, then the time they will take to complete a lap together = LCM (5,6)
prime factorization: 5=5 , 6 =2 x 3
So, LCM(5,6) = 5 x 2 x 3 = 30
Hence, it will take 30 minutes until they complete a lap together.