Question

A=lw+wh+lh, solve for w

Answer 1

Subtract what is to the right of the equal sign form both side of the equation  but any way the answer is 0

Answer 2

      A = lw + wh + lh   Subtract lh from both sides
A - lh = lw + wh          Factor out the w
A - lh = w (l + h)          Divide both sides by (l + h)
$\frac{A - lh}{l + h}$ = w   Switch the sides to make it easier to read
w = $\frac{A - lh}{l + h}$