Question 494261
Since you have the ratio of the width to the length, this is 5 t0 8, then you know that the width is some multiple of 5 and the length is the same multiple of 8.  
We'll let this multiple be x, so you have {{{W = 5x}}} and {{{L = 8x}}}, and the area is expressed as:
{{{(5x)*(8x) = 9000}}} Simplify and solve for x:
{{{40x^2 = 9000}}} Divide both sides by 40.
{{{x^2 = 225}}} Take the square root of both sides.
{{{x = 15}}} This is the multiple, so...
{{{5x = 5(15)}}} = {{{75}}} This is the width, W.
{{{8x = 8(15)}}} = {{{120}}} This is the length, L.