Use logarithms to find the given equation(find x)

9(1.06^5x + 1) = 15

9(1.06^5x + 1) = 15

(1.06^5x + 1) = 15/9
1.06^5x = 2/3
5x log 1.06 = log (2/3)
x = log(2/3) / (5log 1.06)