The answer goes here,
a) We have to tell the time and day which simone has to tell her sister, for picking her up from airport.
b) We have given the day (monday), time(7:00 pm) and total time to reach the destination(18 hours).
c) No such formula will be used here, we will just use our mental ability to solve this question.
d) She will leave at 7:00 pm, day has 24 hours. So, she will be in the flight on monday:
= 24 - (12 + 7) ----------- [12 here means the time of rest of the day,(morning to noon)]
= 24 - 19
= 5 hours
So, she will complete 5 hours of her destination on monday,now the time left is:
= 18 - 5
= 13
= (12 + 1 )hours
So, on tuesday, she will be in the flight for 12 hours (noon) and then on 1:00 pm she will reach the airport, as she needs and extra hour to plane so, the final time is 1:30 pm. And finally, the time she should tell her sister is 1.30 pm.