The formula for exponential growth is f(t) = Aekt
Since the population started at 9000 at t = 0 we have A = 9000 (since e0 = 1)
Now use the given information (that the population was 13000 in 6 years) to figure out what k is equal to
f(6) = 13000 = 9000ek(6)
13/9 = e6k
ln(13/9) = 6k
6k = 0.36772478012
k = 0.06128746335
Now use this value of k to evaluate f when t = 10 in an additional 2 years
f(11) = 9000e11(0.06128746335) use calculator to find answer