How do you calculate log_5(.04)?

${\log}_{5} \left(.04\right)$
$= {\log}_{5} \left(\frac{\cancel{4}}{\cancel{100}} ^ 25\right)$
$= {\log}_{5} \left(\frac{1}{25}\right) = {\log}_{5} \left({5}^{-} 2\right) = - 2 {\log}_{5} 5 = - 2 \times 1 = - 2$