now.. notice the picture
l = 3w
and w it itself :)
the perimeter, or outside border of it
will be, the (left width) + (right width) + (top length) + (bottom length)
and those will be w + w + l + l or 2w + 2l
we know the perimeter is 88cm
so one could say that[tex]\begin{cases}
l=length\to 3w\\
w=width
\end{cases}\implies perimeter=2w+2l
\\ \quad \\
88=2w+2[\ 3w\ ]\impliedby \textit{solve for "w"}[/tex]
once you found "w", to get the length, well, length is 3w, so just do a 3 * w
