The share of the atom present at corner of the cube is $1/8$. The share of the atom at face centre is $1/2.$ Hence, the molecule can be represented as follows,

${\mathrm{X}}_{4\times \frac{1}{8}+1\times 1}{\mathrm{Y}}_{6\times \frac{1}{3}\times \frac{1}{2}}$

$\Rightarrow {\mathrm{X}}_{\frac{1}{2}+1} {\mathrm{Y}}_1$

$\Rightarrow {\mathrm{X}}_{\frac{2}{3}} {\mathrm{Y}}_1$

$\Rightarrow {\mathrm{X}}_{1.5} {\mathrm{Y}}_1$(Empirical formula)

$\Rightarrow {\mathrm{X}}_3 {\mathrm{Y}}_2$.