Then find the sum of the area of the large right triangle at the lower left and the area of the right triangle at the upper right:

Area of the large right triangle at the lower left: 5×(5+7)÷2=30 (square centimeter).

Area of the small right triangle in the upper right corner: 7×7÷2=24.5 (square centimeter).

Sum of areas of two triangles: 30+24.5=54.5 (square centimeter)

Finally, subtract the sum of the areas of two right triangles from the sum of the areas of large and small squares, and the rest is the area of the shadow part:

72-54.5 = 17.5 (square centimeter)