Explanation:
your teacher has told you the first trick already : the figure is actually a combination of 2 simple figures.
so, we need to calculate these sub-areas and add them up for the total area.
the only second trick here is to know that the diameter of a circle is 2×radius. and as we can see on the graphic, the diameter of the half-circle is the width of the rectangle.
so, the area of the rectangle is
5 × (2×2) = 5 × 4 = 20
the area of the half-circle is
pi×r² / 2 = pi×2² / 2 = pi×2 = 6.283185307...
so, the total area of the figure is
20 + 6.283185307... = 26.283185307... ≈ 26.3