Answer:
4.5 or equivalently 4 1/2 or 9/2
All are equivalent
Units are miles/hour
Explanation:
Take any two points on the graph. Divide the change in y values to the change in x values and you get the rate
Chosen points: (0, 0) and (2, 9)
Rate of change = (9-0)/(2-0) = 9/2 = 4.5