Question

First, let's see if the measuring tools work for you. what is the angle of refraction corresponding to the angle of incidence equal to 25∘?

Answer 1

The concept to answer this question can be bought from physics. 
The Snell's law of refraction says that, the ration of sine of angle of incidence to the the sine of angle of refraction is constant for a given media.

This means; 
(sinθ1)/(sinθ2) = k
Where θ1 = angle of incidence and
            θ2 = angle of refraction 
            k = constant

(sinθ1)/(sinθ2) = k
sinθ2 = k/sinθ1
         = k/sin25
         = k/0.422618261
         = 2.366k

The angle of refraction, θ2 = anti-sin(2.366k)