To answer this item, we let x be Jeff's speed when going back home. With this representation, the speed from home to his parents is x + 9. The total time it took him for the trip is 8 hours. The time of each trip can be calculated by dividing the distance by time. Such concept is presented below.
8 hours = 160/x + 160/(x + 9)
The value of x from the equation is 36. Thus, his speeds were 36 miles/h and 45 miles/h.
