Question 739097
We are given Buses to the stadium leave every 12 minutes. Buses to he zoo leave every 15 minutes. Both buses left at 7pm.

The prime factors of 12 are 2*2*3
The prime factors of 15 are 5*3

put the prime factors together and we get

2^2 * 3^2 * 5 = 180

note that both 15 and 12 divide 180 so

the next time the buses leave at the same time is 180 minutes from 7pm  ( given starting time for the buses)

7pm + 3 hours = 10pm for the next time the stadium and zoo buses leave at the same time