Answer
7
Work Step by Step
From the definition of the logarithmic function on page 456, we know that $y=log_{b}x$ is equivalent to $b^{y}=x$(for $x\gt0$, $b\gt0$, and $b\ne1$).
Therefore, $log_{5}5^{7}=7$, because $(5)^{7}=5^{7}$.
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