find the dimension of a rectangle with a perimeter of 54 cm if its length is 3cm less than twice its width also find the area of the rectangle

Set up a system of equations:

Let
W=width
L=length
then
Perimeter =
54 = 2(L+W) ...(1)
L=2W-3 ...(2)

Solve W by substituting (2) in (1), and hence solve for L.