Question 951874
On day 1, Jane drives 180 mi/90mph=2 hours
On day 2, she drives 60 mi/15 mph=4 hours 
Total time driving 2 hrs+4 hrs=6 hrs
Total distance=180mi+60mi=240mi
Overall Jane drove 240mi/6hrs=40 mi/hr ANSWER: Jane's average speed over the two days was 40 miles per hour.