Answer
$\log_b \dfrac{w^2}{zy^4}$
Work Step by Step
Using the properties of logarithms, the given expression, $
2\log_b w-\log_b z-4\log_b y
,$ is equivalent to
\begin{array}{l}\require{cancel}
2\log_b w-(\log_b z+4\log_b y)
\\\\=
\log_b w^2-(\log_b z+\log_b y^4)
\\\\=
\log_b w^2-(\log_b zy^4)
\\\\=
\log_b \dfrac{w^2}{zy^4}
.\end{array}
