If you study the diagram, you will see that it looks like someone took a bite (in the shape of a small rectangle) out of a large rectangle. So to find the area of the complex diagram, we simply subtract the area of the small rectangle (the bitten off portion) from the whole large rectangle.
Area of large rectangle = 69 * 31 = 2139
Area of small rectangle = 23 * 12 = 276
Area of complex figure = area of large rectangle - area of small rectangle = 2139 - 276 = 1863 square meters
Hope that helps. Let me know if you have any questions.
