Evaluate the function at 2. That is f(2).
Evaluate the function at 0. That is f(0).
the average rate of change from 0 to 2 is (f(2) - f(0))/(2 - 0)
f(x) = 120(0.1)^x
f(2) = 120(0.1)^2 = 120 * 0.01 = 1.2
f(0) = 120(0.1)^0 = 120 * 1 = 120
average rate of change = (1.2 - 120)/(2 - 0) = -118.8/2 = -59.4