width = 82 feet, length = 123 feet
First, write down equations that express what you've been given.
w = 2/3 l
p = 410
p = 2(w+l)
Since we have an expression that defines w in terms of l, substitute for w, the expression. Also substitute the known value for p in the expression.
p = 2(w + l)
410 = 2( 2/3 l + l)
Combine the l terms
410 = 2( 5/3 l)
Multiply
410 = 10/3 l
Multiple both sides by 3
1230 = 10 l
Divide both sides by 10
123 = l
So we now know the length is 123 feet.
So plug in the known value of l into the formula w = 2/3 l to get the width
w = 2/3 123 = 82