Answer
$w = \frac{P-2l}{2}$
Work Step by Step
$Solve$ $the$ $equation$ $for$ $the$ $indicated$ $variable:$
$P = 2l + 2w;$ $for$ $w$
Solve for $w$
Subtract both sides by $2l$
$P-2l = 2l+2w-2l$
Simplify
$P-2l = 2w$
Divide both sides by 2
$\frac{P-2l}{2} = \frac{2w}{2}$
Simplify
$\frac{P-2l}{2} = w$
$w = \frac{P-2l}{2}$