Question

refractive index of glass with respect to air is 1.5 fund the refractive index of air with respect to glass​

Answer 1

(refractive index of glass with respect to air)×(refractive index of air with respect to glass)=1 . this is normally thought in your class 9or 10. so refractive index of air with respect to glass=1/1.5 =0.67.