Question

the line a arrives at the bus stop every 25 min and the line b bus arrives every 15 min they both at the bus stop right now, in how mnany min will they both be at the bus stop again

Answer 1

Not sure if it is right but,
Time taken for line a to arrive on stop= 25 minutes.
Time taken for line b to arrive on stop=15 minutes.
So we see that there is a difference of 10 minutes between them.
This means that line arrive and be together with line b, after 10 minutes of when line b arrives.
So 25-15 =10 minutes will take for them to be together at the stop again.