What is the formula of the compound in which element Y forms hcp lattice and atoms of X occupies 2/3rd of the tetrahedral voids?

In hcp lattice every lattice contains 6 atoms. And the no od tetrahedral voids forms is always twice the no. of atoms. So the no of td voids = 12. But only 2/3 rd of voids are occupied.

Therefore, 2/3rd of 12 = 8.

So Y : X = 6:8 = 3:4

So the formula of compound will be X₄Y₃