Answer:
Option C is correct
The value of y is, 

Explanation:
Exterior Angle theorem states that the sum of the measures of the two non-adjacent interior angles of the triangle is equal to the measure of an exterior angle.
Label the figure: 
In triangle ABC, BC is produced to D, then 
 is the exterior angle , 
 and 
 are the two interior opposite angle.
i.e, 

From the given figure: 
 and 


Then, by the Exterior angle theorem, we calculate the value of y;

Combine like terms:
 
on simplify:

therefore, the value of y is, 
