# How do you use log_10 5=.6990 and log_10 7=.8451 to evaluate the expression log_10 (7/5)?

Use the implied $\log$ for ${\log}_{10} \mathmr{and} \log \left(\frac{m}{n}\right) = \log m - \log n$.
$\log \left(\frac{7}{5}\right) = \log 7 - \log 5 = 0.8451 - 0.6990 = 0.1461$.