im getting 12 but i think its wrong

Notice that when x = -1, y = f(-1)  =  3

And when x = 1, y = f(1)  = 27

So.....average rate of change is

[ f(1) - f (-1) ]

___________  =

     1 - (-1)

[ 27 - 3 ]

______   =

      2

24

__   =

 2

12   ⇒   GOOD JOB!!!

thank you !!