If $\frac{4}{3}$ and $\frac{3}{2}$ be respectively the absolute refractive indices of water and glass, then the refractive index of glass relative to water is

Let the absolute refractive index of water be $n_w=\frac{4}{3}$ and that of glass be $n_g=\frac{3}{2}$.The relative refractive index of glass with respect to water (${}^w{n}_g$) is given by the ratio of the absolute refractive index of glass to the absolute refractive index of water:
$${}^w{n}_g=\frac{n_g}{n_w}$$
Substitute the given fractional values:
$${}^w{n}_g=\frac{\frac{3}{2}}{\frac{4}{3}}=\frac{3}{2}\times \frac{3}{4}=\frac{9}{8}$$