The centroid of the semicircular area of radius a lies at a distance of 4a/(3*pi) from the center along the axis of symmetry. The right-angled isosceles triangle removed has its hypotenuse as the diameter, meaning its altitude is a, and its centroid lies at a distance of a/3 from the center along the same axis. Taking moments about the center for the remaining area, (pi*a^2/2)(4a/(3*pi)) - (a^2)(a/3) = ((pi*a^2/2) - a^2)x. Simplifying the left side gives (2a^3/3) - (a^3/3) = a^3/3. Equating this to the right side and solving for x results in x = a / (3(pi - 1)).