The length of a rectangle is twice its width. if the perimeter of the rectangle is 60 yd , find its area.

Hello : 
let : x the length   y the width
 x = 2y...(1)
2(x+y) =60  ..(2)
 subsct in (2) : 2(2y+y)=60
y = 10 yd
x= 20  yd
the  area is : xy  = 10× 20 = 200 yd²

I’d say letter a..

Where’s the problems ? ?