Math  I really need help, please.
posted by Lacey on .
A town has a population of 8400 i 1990. Fifteen years later, it's population grew to 12500. Determine the average annual growth rate of this town's population.
I really don't understand this problem. I've been going at it for hours and all I've come to is that the equation should be P=8400(1+x)^15 x being the annual percentage, so then, I substitute 12500 for P. but I don't know where to go from there. Please, I really need help on this.

12500=8400(1+x)^15
divide both sides by 8400
1.488=(1+x)^15
take the fifteenth root of each side
1.488^(1/15)=1+x
1.027=1+x 
oh, thank you so much!

(1.0271)x100= 2.7%