Ray optics and optical instruments class 12 physics

Question

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The question says the ray is incident at 15 with the refracting surface 

In school we were taught the incidence angle =90-15=75

But most of the answers consider the angle of incidence as 15 

So which one do we consider? 

Answer 1

We know that

s = i + l - A

55 = 15 + l - 60

115 = 15 + l

l = 115 - 15

l = 100°