Answer:
[tex]w=\dfrac{P}{2}-\ell[/tex]
Step-by-step explanation:
Divide by 2, then subtract the length.
[tex]P=2(\ell+w)\\\\\dfrac{P}{2}=\ell+w \quad\text{divide by 2}\\\\\dfrac{P}{2}-\ell=w \quad\text{subtract $\ell$}\\\\w=\dfrac{P}{2}-\ell \qquad\text{your formula for $w$}[/tex]
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A script L is sometimes used to avoid confusion with I (eye) or 1 (one). It can look like an "e".
