Robert drove at a constant rate of 60 miles per hour. He decided to drive an additional 15 miles to visit his favorite restaurant along the way for a total of 225 miles. Find the number of hours Robert spent driving. Write your answer in decimal form.
Robert drove 225-15 = <<225-15=210>>210 miles from his house to his favorite restaurant.
The number of hours Robert spent driving is 210/60 = <<210/60=3.5>>3.5 hours. Answer: \boxed{3.5}.