Answer:
[tex]\boxed{\sf B)\: w=\cfrac{p}{2}-l}[/tex]
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Step-by-step explanation:
[tex]\sf p=2\left(l+w\right)[/tex]
✰ Switch sides:
[tex]\longmapsto\sf 2\left(l+w\right)=p[/tex]
✰ Divide both sides by 2:
[tex]\longmapsto\sf \cfrac{2\left(l+w\right)}{2}=\cfrac{p}{2}[/tex]
[tex]\longmapsto\sf l+w=\cfrac{p}{2}[/tex]
✰ Subtract l from both sides:
[tex]\longmapsto\sf l+w-l=\cfrac{p}{2}-l[/tex]
[tex]\longmapsto\sf w=\cfrac{p}{2}-l[/tex]
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