Answer
$x=\dfrac{1}{20}=0.05$
Work Step by Step
Recall the definition of a logarithm (pg. 451):
$\log_{b}{x}=y$ iff $b^y=x$
Applying this definition to our equation (with $b=10, y=-1, x=2x$), we get:
$10^{-1}=2x$
$\dfrac{1}{10}=2x$
$\dfrac{\frac{1}{10}}{2}=\dfrac{2x}{2}$
$x=\dfrac{1}{20}=0.05$
We confirm that the answer works:
$\log_{10}2*0.05=-1$
$\log_{10}0.1=-1$
$-1=-1$
