#### Answer

$L=\dfrac{P-2W}{2}$

#### Work Step by Step

Using the properties of equality, in terms of $
L
,$ the given formula, $
P=2L+2W
,$ is equivalent to
\begin{array}{l}\require{cancel}
P-2W=2L
\\\\
\dfrac{P-2W}{2}=\dfrac{2L}{2}
\\\\
L=\dfrac{P-2W}{2}
.\end{array}