Answer: y= 50
Explanation:
The angles that are formed inside the two lines and on opposite sides of the transversal are known as alternate interior angles.
Consider the given figure , we can see that line b and line c are intersected by a transversal so by the definition of alternate interior angles,
The alternate interior angles formed =
and

Since we are given that two parallel lines are crossed by a transversal.
Then the alternative interior angles must be congruent.

Hence, the value of y= 50