Light intensity of 2 Wm^-2 is travelling through air (n = 1.0) and is normally incident on a dielectric surface. If the intensity of the reflected light is 0.3 Wm^-2 what is the refractive index of the dielectric material?

The correct answer is 2.26
I have no clue as to how to begin this question.

Light of intensity 1 Wm-^2 is incident on two dielectric layers that have been stuck together. Calculate the intensity of the light that is transmitted into material 2 (n = 1.2) (attenuation in material 2 can be ignored). Material 1 has attenuation coefficient α = 6 m^-1 and n = 1.7.

Please show your working, thanks.
The correct answer is 0.673Wm^-1