Simplify log 343/125
Using identity, $\log \left( \frac{M}{N} \right) = \log M - \log N$
So, $\log \left( \frac{343}{125} \right) = \log 343 - \log 125$
$\log 343 - \log 125 = \log (7^3) - \log (5^3) = 3 \log 7 - 3 \log 5$
Therefore, log 343/125 = $3 \log 7 - 3 \log 5$