the rate of change is the same as the slope...u can use the slope formula : (y2 - y1) / (x2 - x1), with 2 sets of points...or....according to ur graph, they want to know how many miles u can go for 1 hr. y/x.....60/1....so they can go 60 miles in 1 hr...60/1 is ur unit rate.
To find the unit rate, you should find the slope. In order to find the slope of this line, use the rise/run between two points technique. For example the rise/run between points (2,120) and (3,180) is 60/1, or 60. This means that in one hour the family's car drives 60 miles.
