Atoms of elements `B` from hcp lattice and those of element `A` occupy two-thirds of tetrahedral voids. What is the formula of the compound formed by elements `A` and `B`?

In a compound ,atoms of element Y from ccp lattice and those of element X occupy 2/3rd tetrahedral voids.The formula of the compound will be:

Atoms of element P form ccp lattice and those of the element Q occupy 1/3rd of tetrahedral voids and all octahedral voids. What is the formula of the compound formed by the elements P and Q?

In a compound atoms of element Y form cup lattice and those of element X occupy 2//3^(rd) of lettabedral voids .The foemula of the compound will be