Answer
2.72
Work Step by Step
We are given $log_{b}2=.43$ and $log_{b}3=.68$.
We know that $log_{b}x^{r}=rlog_{b}x$ (where $x$ and $b$ are positive real numbers, $b\ne1$, and $r$ is a real number).
Therefore, $log_{b} 81=log_{b}3^{4}=4log_{b}3=4\times.68=2.72$.