"What is the area? You should be able to solve this"

[Albert Chan]

There is another way to solve top right area without inner square:

Let P = (x,y), inside the square with side = 2
With P, square splitted into 4 triangles, all with base=2, thus triangle area = height

Triangle Area: Left, Bottom, Right, Top = x, y, 2-x, 2-y

SB = 1/2 (Left + Bottom) = (x + y)/2
SX = 1/2 (Right + Top) = 2 - (x + y)/2

SB + SX = 2
SA + SC = 2*2 - (SB + SX) = 4 - 2 = 2

SX = 2 - SB = SA+ SC - SB = (16 + 32 - 20) cm^2 = 28 cm^2