Answer: length of the rectangular firls = 50
and the breadth = x-20m= 50-20m =30m
Explanation:
The perimeter of a rectangle is given as 2(l+b) 
 let the length be represented as x
 such that the breadth = x-20m
 so our expression for the perimeter of the rectangular firls becomes 
 Perimeter = 2l+ 2b
 160= 2x + 2 ( x-20)
 160= 2x+ 2x-40
160+40 =4x
200= 4x
x= 200/4
x= 50
 So the length of the rectangular firls = 50
and the breadth = x-20m= 50-20m =30m