6 years ago t = 0
1500 = A0 e^0
Ao = 1500
when t = 6 A = 900 so
900 = 1500e^6k
e^6k = 900/1500 = 0.6
6k = ln 0.6
so k = -0.08514
when A = 100
100 = 1500 e^-0.08514t
e^-0.08514t = 0.066667
t = 31.8 or 32 years
Number of years from now = 32 - 6 = 26 years answer