Answer
" The logarithm of a power of the base is the exponent of that power"
Work Step by Step
$b^{x}$ is a power of b, with exponent x.
so the formula can be read as
" The logarithm of a power of the base is the exponent of that power"
This stems from the definition (see p.456)
The logarithm of $b^{x}$ with base b is a number y,
$y=\log_{b}b^{x}$,
such that $b^{y}=b^{x}.$
So, by the basic property of exponential functions,
$y=x,$
$\log_{b}b^{x}=x$
