## Precalculus (6th Edition) Blitzer

The required value is $120\text{ decibels}$
According to the given information in the question, $D=10\log \left( \frac{I}{{{I}_{o}}} \right)$ And $I={{10}^{12}}{{I}_{o}}$ Plug in the value: $D=10\log \left( \frac{{{10}^{12}}{{I}_{o}}}{{{I}_{o}}} \right)$ Use $\log \left( {{a}^{b}} \right)=b\log \left( a \right)$ to obtain: \begin{align} & D=10\cdot 12\log \left( 10 \right) \\ & D=120 \end{align}