remember, you can do anything to an equation as long as you do it to both sides
try and isolate the variable you are solving for and divide it by its constant
p=2l+2w
minus 2l from both sides
p-2l=2w
divide both sides by 2
[tex]\frac{p-2l}{2}=w[/tex]
[tex]w=\frac{p-2l}{2}=w[/tex]
which can also be simplified to
[tex]w=\frac{p}{2}-l[/tex]
