we have
[tex]s=2(lw+lh+wh)[/tex]
Solve for w means that clear variable w
[tex]s=2(lw+lh+wh)\\s=2lw+2lh+2wh[/tex]
Group terms that contain the variable w, and move the other terms to the opposite side of the equation
[tex](s-2lh)=(2lw+2wh)[/tex]
Factor the variable w
[tex](s-2lh)=w(2l+2h)[/tex]
Divide both sides by [tex](2l+2h)[/tex]
[tex](s-2lh)/(2l+2h)=w(2l+2h)/(2l+2h)[/tex]
[tex]w=(s-2lh)/(2l+2h)[/tex]
therefore
the answer is
[tex]w=(s-2lh)/(2l+2h)[/tex]
