Diana needs to bike 10 miles to get home.  She can bike 3 mph for two hours before she gets tired, and she can bike 1 mph until she gets home.  How long will it take Diana to get home?
In the first part of her trip, Diana will cover 2 hours * 3 mph = <T>multiply(2, 3)=6 miles.
In the second part of her trip, Diana will need to cover an additional 10 miles - 6 miles = <T>subtract(10, 6)=4 miles.
To cover 4 miles * 1 mph = will take Diana <T>multiply(4, 1)=4 hours.
Total biking time to get home for Diana will be 2 hours + 4 hours = <T>add(2, 4)=6 hours.
