Answer:
-2
Step-by-step explanation:
The rate of change is
roc = f(x2) - f(x1)
---------------
x2 -x1
x2 is the last point or 15
x1 is the first point or 10
f(15) = 10 from the graph
f(10) = 20 from the graph
roc = f(15) - f(10)
---------------
15-10
roc = 10 - 20
---------------
15-10
roc = -10
--------
5
roc = -2
