[tex]\bf \textit{area of a rectangle}\\\\
A=LW~~
\begin{cases}
L=length\\
W=width\\
---------\\
A=1764\\
W=\stackrel{\textit{13 more than L}}{L+13}
\end{cases}\implies 1764=LW
\\\\\\
1764=L(L+13)\implies 1764=L^2+13L\implies 0=L^2+13L-1764
\\\\\\
0=(L+49)(L-36)\implies L=
\begin{cases}
-49\\
\boxed{36}
\end{cases}[/tex]
well, since the length can't be a negative value, it can't be -49.
now, you know what the length is, since is just L + 13.
the perimeter is of course length + length + width + width, so that'd give us
36 + 36 + 49 + 49.
