Question 104940
P=120 feet
W/L=5/7
The perimeter of a rectangle is 
{{{P=2W+2L}}}
You also know
{{{W/L=5/7}}}
{{{W=5L/7}}}
Use that in your perimeter equation,
{{{P=2W+2L=120}}}
{{{2(5L/7)+2L=120}}}
{{{10L/7+14L/7=120}}}
{{{24L/7=120}}}
{{{L=120*7/24}}}
{{{L=35}}}
From your previous equation,
{{{W=5L/7}}}
{{{W=5(35)/7}}}
{{{W=25}}}
Check your answer. 
{{{W/L=5/7}}}
{{{25/35=5/7}}}
{{{5/7=5/7}}}
Good, now check perimeter.
{{{2W+2L=120}}}
{{{2(25)+2(35)=120}}}
{{{50+70=120}}}
{{{120=120}}}
Good answer.  
W=25 feet, L=35 feet.