So if the driveway is 45 feet long and he clears 6 feet per hour, we can divide 45 by 6 to find out how many hours it will take for him to clear the driveway and that is essential
45 / 6 = 7.5
45 feet / 6 feet per hour = 7.5 hours to clear the driveway
So now we know that the graph will end when he clears the driveway
If we know he will finish after 7.5 hours then find the graph that ends at the 7.5 hour mark, and that is the last one