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