Inter arrival time of busses of route 49U of
Chicago Bus System follows an exponential distribution. The probability that a bus arrives in 10
minutes is 0.2. Now Mr. JJ has waited
for the bus for 20 minutes; however the bus did not arrive. What is the
probability that he will get the next bus in 10 minutes from now? (Attached picture for the chapter used for this question, "The Normal Distribution") Thank you.

Thank you for the opportunity to help you with your question!

the question has nothing to do with normal distribution because it is given that the waiting time follows an exponential distribution, the characteristic of exponential distribution is it is Memoryless, the future probability does not depends on what had happen in the past. Thus the probability is just 0.2

Please let me know if you need any clarification. I'm always happy to answer your questions.