What are the dimensions of a rectangle with a perimeter of 70 and a length to width ratio of 4 to 5?

Hello : 
let : x the length   and  y  the width
the perimeter is : 2(x+y)
2(x+y) = 70  and : x/y =4/5
x+y = 35 (1)
x = (4/5)y ... (2)
subsct in : (1)
 (4/5)y +y = 35 
4y+5y = 175
9y = 175
y = 175/9
in (2) : x = (4/5)(175/9) = 140/9