how can we find angle between incident & emergent ray when a ray of light passes through the 3 media of diff refractive index?

We know , for a start , the angle of incident ray on the 1^stmedium. To solve the problem we need to know the refractive index of all the three medium here. If we know the refractive index of all the three medium then we can calculate the angle of refraction of each of emergent ray .Emergent ray from the interface of 1^stand 2^ndmedium becomes the incident ray for interface for 2^ndand 3^rdmedium.
Through this we can caluclate the angle between the emergent ray and the incident ray.