Answer: 2 hours
Explanation: As Jenny left the hospital 3 hours before Kristin and was travelling at 30 km/hour she should have gotten 90 km before Kristin started driving. As Kristin was travelling at 75 km/hour she will get 45 km closer to Jenny every hour (30-75= (-45)). 45 km/90 km= 2 hours to catch up.
