Remark
You have to make an assumption here. I know of no other way to do the problem than by making the assumption that 10 * 14 figure is a rectangle. If that is not true, the problem is not solvable.
Step One
Find the length of the shaded area.
The length will be the length of the hypotenuse of a right triangle formed by the two smaller sides = the hypotenuse.
a = 4
b = 12
c = ????
Length
L = square root (a^2 + b^2)
L = √(4^2 + 12^2)
L = √(16 + 144)
L = √160 = √(4*4 * 10)
L = 4√(10)
Width
The width is done the same way.
a = 6
b = 2
w = c = ??
w = √(6^2 + 2^2)
w = √(36 + 4)
w = √40
w = √(2 * 2 * 10)
w = 2 √ 10
Area
Area = L * W
Area = 4√10 * 2√10
Area = 8 * 10
Area = 80
