Answer
$1-\log_{7}{x}$
Work Step by Step
RECALL:
(i) $\log_b{\frac{M}{N}}=\log_b{M} - \log_b{N}$ (Quotient Rule).
(ii) $\log{x}=\log_{10}{x}.$
(iii) $\log_b{b}=1.$
Use the quotient rule with $M=7$ and $N=x$ to obtain
$\log_7{7} - \log_7{x}.$
Use rule (iii) above to obtain
$1-\log_{7}{x}.$
