Consider the following silicates:

(a) $\mathrm{BaTi}\left({\mathrm{Si}}_3{\mathrm{O}}_9\right)$     (b) ${\mathrm{ZnCa}}_2{\mathrm{Si}}_2{\mathrm{O}}_7$

Calculate the ratio of total number of monovalent oxygen atoms in first silicate to total number of divalent oxygen atoms in second silicate.

For $\mathrm{BaTi}\left({\mathrm{Si}}_3{\mathrm{O}}_9\right)$, the number of monovalent oxygen atoms $\left(\mathrm{X}\right)$is 6 and the number of divalent $\mathrm{O}$ atoms $\left(\mathrm{Y}\right)$ is 3.

For ${\mathrm{ZnCa}}_2{\mathrm{Si}}_2{\mathrm{O}}_7$​ the number of monovalent oxygen atoms $\left(\mathrm{X}\right)$ is 6 and the number of divalent $\mathrm{O}$ atoms $\left(\mathrm{Y}\right)$ is 1.
Hence, total X=6+6=12 and total Y=3+1=4