Answer
$\log{10^7} = 7$
Work Step by Step
The given expression involves a common logarithm, meaning that no base is written in, so its base is 10.
RECALL:
$\log{y}=x \longrightarrow 10^x=y$
Let
$\log{10^7}=x$
Use the rule above, with $y=10^7$, to obtain:
$10^x=10^7$
Use the rule "If $a^x=a^y$, then $x=y$" to obtain:
$x=7$
Therefore,
$\log{10^7} = 7$