Answer
$\log_{b}{343}=3$
Work Step by Step
RECALL:
$b^y=x \longleftrightarrow \log_b{x} =y .$
Use the definition above to obtain
$b^{y} = 343 \longrightarrow \log_{b}{343}=3.$
Thus, the equivalent logarithmic form of the given expression is
$\log_{b}{343}=3.$