This is what I do and don't know what's wrong or what to do next:

f(x) = ac^x + k

f(x) = ac^x

f(x) = 5.5(1.9)^x

9/5.5 = 1.9^x

log (9/5.5)/log(1.9) = x

x = 0.767271953

What am I doing wrong OR what does that small number mean?

Any help would be greatly appreciated!

Thanks in advance!