Answer: The average rate of change is 19.
Step-by-step explanation: The given function is

We are to find the average rate of change from x = 5 to x = 8.
We know that if for a function f(x), f(a) = b and f(c) = d, then the average rate of change from x = a to x = c is given by

For the given function, we have

Therefore, the average rate of change from x = 5 to x = 8 will be

Thus, 19 is the required average rate of change.