Answer:
2:50pm
Explanation:
You have to find the least common multiple (LCM) between the 3 times. If you don't know what is the LCM, just say it and I'll try to explain for you in the comments.
10, 35, 40 have as LCM the number 560
So it means they'll leave together 560 minutes after 5:30am
One hour is 60 minutes, so we can divide 560 by 60 to find the time in hours:
560/60 = 9 hours and 20 minutes (the rest of the division will be the minutes)
So, they'll leave together at 2:50pm