Let $A$, $B$, $C$, be three points on a line such that $AB = 2$ and $BC = 4$. Semicircles are drawn with diameters $\overline{AB}$, $\overline{AC}$, and $\overline{BC}$. Find the area of the shaded region.
Here is the visual image of what you have described...
The question becomes....what "shaded area" are you referring to ???