## Precalculus (10th Edition)

$8.1$ magnitude
With $M(x)=\log\frac{x}{x_0}$, $x=125,892$, and $x_0=10^{-3}$, then plugging these values in gives: $M(10^{-7})=log\frac{125,892}{10^{-3}}=8.1$