Explanations
The fastest way to calculate the area of the shaded part is not to calculate the areas of the separate shaded parts of the squares but rather to:
A. Calculate the total area of the three squares: 100 + 64 + 8 = 180.
B. Calculate the area of the big non-shaded triangle: 1/2 x (10+8+4) x 10 = 110.
C. Deduct (B) from (A): 180 - 110 = 70 (sq units).