Please solve question no 7

Please solve question no 7 v) o O O 0 Q) o O

Dear student,

Na = cube center = 1 atom
0 = edge center = 3 atoms (12 edges × 1/4 atom)
w = cube corners = 1 atoms (8 corners × 1/8 atom) 

N.a.: o : w = 1 : 3 : 1
3Na : 2O : 3W = 6:6:6 ( equal proportions take lcm)

molecular formula $N{a}_3{O}_2{W}_3$

Regards