Suppose: a small rectangle is x in width and y in length. From the left picture, 5x=3y, that is, y=5x/3.

S large square =(2x+5x/3)2

Small square = 1

So: s big -s small = 8 s small rectangle

(2x+5x/3)2— 1=8x 5x/3

( 1 1x/3)2— 1 = 40 x2/3

12 1x 2/9— 1 = 40 x2/3

12 1x 2/9—40 x2/3 = 1

x2/9= 1

x2=9

X=3

So: y=5x/3=5.

That is, the width of the small rectangle is 3 and the length is 5.