Question 880773
First calculate the place Sharon is at at 9 15. 
80 km/h over 1 hour and 15 minutes = 100km
Now you know that Michelle rode the other 120km in 45 minutes.
120km in 45 minutes = 160 km/h
So a)Michelle's average speed was 160km/h

for b:
Again first calculate the place sharon is at at 9 15.
80 km/h over 1 hour and 15 minutes = 100km.
Now you know that she will drive the other 120 km at 90 km/h
120 km over 90 km/h = 1 hour and 20 minutes.
1 hour and 20 min + 1 hour and 15 min = 2 hours and 35 minutes.
So b) Sharon reached town Y at 10:35.