A solid has a structure in which W atoms are located at the corners of a cubic lattice, O atoms at the center of edges and Na atom at center of the cube. The formula for the compound is

In a unit cell, W atoms are at eight corners of the cube. Each corner atom contributes one eight to the unit cell. The contribution of W atoms to the unit cell =$8\times \frac{1}{8}=1$

O-atoms at the center of 12 edges. Each edge center atom contributes one fourth to the unit cell. The contribution of O atoms to the unit cell = $\frac{1}{4}\times 12=3$

Na atom is at the center of the cube. Body center atom contributes one to the unit cell. The contribution of Na atoms to the unit cell =1

The ratio of number of atoms in the cube W:O:Na=1:3:1

Hence, formula =NaWO₃​.