algebra
posted by Tony .
A town has a population of 8400 in 1990. Fifteen years later, its population grew to 12500. Determine the average annual growth rate of this town's population. How do i solve this using applications of exponential functions?

12500=8400(R)^15
ln12500=ln8400+15lnR
solve for R 
it doesnt work,
the answer is approximately 2.7%
:(