W = width of the rectangle
L = length, W + 3
[tex]\bf \textit{perimeter of a rectangle}\\\\
P=2(L+W)~~
\begin{cases}
L=length\\
W=width\\
------\\
P=22\\
L=W+3
\end{cases}\implies 22=2[(W+3)+W]
\\\\\\
\cfrac{22}{2}=2W+3\implies 11=2W+3\implies 8=2W
\\\\\\
\cfrac{8}{2}=W\implies 4=W[/tex]
