A square shaped hole of side l = (a)/(2) is carved out at a...

${X}_{a} = \dfrac{A \cdot X - A \cdot X1}{A - {A}_{1}} = \dfrac{{\pi a}^{2} \times 0 - \dfrac{{a}^{2}}{4} \times \dfrac{a}{2}}{{\pi a}^{2} - \dfrac{{a}^{2}}{4}}$
$= \dfrac{- {a}^{3} / 8}{\left(\pi - \dfrac{1}{4}\right){a}^{2}} = \dfrac{- a}{2 ( 4\pi - 1 )} = \dfrac{- a}{8\pi - 2} = - \dfrac{a}{23}$
$x = 23$