Answer
$\log_b1$ is equal to 0, so $\log_b7-\log_b1 = \log_b7 - 0 = \log_b7$.
Work Step by Step
As long as the value of $b$ is greater than $0$ and not $1$, $\log_b1$ is always equal to 0. This is because $b^x=1$, where $b$ is greater than $0$ and not $1$, is only true when $x=0$.
