The perimeter of a rectangle is given by:
[tex]P=2l+2w[/tex]Where:
P = perimeter = 252 ft
w = width = 5 ft
l = lenght
Then, substitute the values:
[tex]252=2l+2(53)[/tex]And solve for l:
[tex]\begin{gathered} 252=2l+106 \\ 252-106=2l+106-106 \\ 146=2l \\ \frac{146}{2}=\frac{2l}{2} \\ l=73 \end{gathered}[/tex]Answer: length = 73 ft