We have three rectangles on the figure, with the next dimensions:
13x7, 4x3, and 2x1 cm
The area of a rectangle is computed as follows:
A = base*height
Then, the area of the different rectangles are:
A1 = 13*7 = 91 square cm
A2 = 4*3 = 12 square cm
A3 = 2*1 = 2 square cm
Finally, the area of the shaded region is:
A1 - A2 - A3 = 91 - 12 - 2 = 77 square cm
