Alright, so I, ugh failed my math test today...

but for the life of me or any of my classmates we couldnt figure this out...

...the diagonal of a rectangle is $\displaystyle 5squareroot2$ the area is 20...what is the width of the rectangle....

You don't really HAVE to answer the question (seeing as how the units over), but im dieing to know the answer...or atleast the steps.