Because the question mentioned that all the 3 shapes are squares, hence all the sides of each shape will have the same length. This clue therefore allows you to be able to find the length of each shape, which are 6cm, 4cm and 3cm respectively. Now, find the total area of the entire figure, which isnthe sum of the areas of each shapes added uo together. In the figure, the 2 unshaded portion forms 2 different triangles, and the areas of the unshaded portion can be found using 1/2 × base× height formula. Since area of shaded portion= total area- area of unshaded portion, you can thus find the area of the shaded part