we have the following:
[tex]\begin{gathered} p=2\cdot l+2\cdot w \\ l=w+12 \\ p=160 \end{gathered}[/tex]replacing:
[tex]\begin{gathered} p=2\cdot(w+12)+2\cdot w \\ 160=2\cdot w+24+2\cdot w \\ 4\cdot w=160-24 \\ w=\frac{136}{4} \\ w=34 \end{gathered}[/tex]therefore, the width is 34 feet, the length:
[tex]\begin{gathered} l=34+12 \\ l=46 \\ \end{gathered}[/tex]the length is 46 feet