Remember the change of base formula when solving a logarithm that is not base 10.
Log(base 3) 11 = Log 11/Log 3
It's easy to see how this comes about when rewriting the log in exponential form and then solving for y.
y = log(base 3) 11
3^y = 11
Take the log of both sides to get
log(3^y) = log 11
ylog 3 = log 11
y = log11/log3
Instead of having to rewrite as an exponential equation and solving, simply use the change of base formula. In general
Log(base b)a = Log a/Log b