We know that the area of a square is the side squared, so we can use the inverse of this formula to say the side of a square is the square root of the the area. This gives us√33 and √44 as the side lengths of the red and green squares respectively. Next, we use the pythagorean theorem to find the other side of the white right triangle, which is also a side of the blue square. So:
(√44)^2 - (√33)^2 = side^2
44 - 33 = side
side^2 = 11
side = √11
To find the area of a square, you just square the side, so we get (√11)^2 which is just 11 units^2.
