In order to determine the length of the given rectangle, Solve the equation for the perimeter of the rectangle for l and replace w=55ft and P=260ft, and simplify:
[tex]\begin{gathered} P=2l+2w \\ 2l=P-2w \\ l=\frac{P-2w}{2} \\ l=\frac{260ft-2(55ft)}{2} \\ l=\frac{260ft-110ft}{2} \\ l=\frac{150ft}{2}=75ft \end{gathered}[/tex]Hence, the length of the rectangle is 75ft