Answer
$4$
Work Step by Step
RECALL:
(i) $\log_b{M} - \log_b{N} = \log_b{\frac{M}{N}}.$
(ii) $\log_b{b^x}=x.$
Use rule (i) above with $M=405$ and $N=5$ to obtain
$\log_3{\frac{405}{5}}
\\=\log_3{81}
\\=\log_3{3^4}.$
Use rule (ii) above to obtain
$4.$
