#### Answer

$l=2w-P$

#### Work Step by Step

$\bf{\text{Solution Outline:}}$
To solve the given equation, $
w=\dfrac{P+l}{2}
$ for $
l
,$ use the properties of equality to isolate the variable.
$\bf{\text{Solution Details:}}$
Using the properties of equality to isolate the variable, the equation above is equivalent to
\begin{array}{l}\require{cancel}
w=\dfrac{P+l}{2}
\\\\
2(w)=2\left( \dfrac{P+l}{2} \right)
\\\\
2w=P+l
\\\\
2w-P=l
\\\\
l=2w-P
.\end{array}