L = [tex]\frac{P - 2W}{2}[/tex]
isolate the term in L by subtracting 2W from both sides
P - 2W = 2L
divide both sides by 2
[tex]\frac{P - 2W}{2}[/tex] = L
dividing each term on the numerator by 2 gives an alternative form
L = [tex]\frac{P}{2}[/tex] - W
