I can give it a try, I did this in about 5 minutes because I have to leave to a friends house real quick but,
You have total area- inner area.
The inner area is the circles , which we denote in terms of area for circles = pi*x^2/2 + pi*x^2 + pi*x^2/2 = 3pi*x^2.
Now total area of squares = X+X+x+X = 4x.
Now, to get shaded area _> 4x - 3*pi*x^2 = x(4-3*pi*x)
