City hoppa run two buses starting from the same bus stop. one has a route of 25 minutes. & the other has a route of 55 minutes. both buses leave the bus stop at 6.00am and run continously.
what is the next time that the buses will at the same stop together?

You have to find the least common multiple (lcm) of 25 and 55.

To find lcm you have to seperate 25 and 55 to prime factors:
25= 5 * 5
55= 5 * 11
Both numbers has one same prime factor which is 5 (bolded). 
LCM is a multiplication of unique prime factors and one from each pair of the same prime factors, see it below:


This means that the buses are going to meet at the same stop after 275 minutes from their start.
275 minutes are 4 hours and 35 minutes.
Buses start at 6.00 am, add 4 hours and 35 minutes to receive the time of their meeting which is 10.35 am.