1. **State the problem:** We have two parallel lines cut by a transversal, creating angles of 72° and y° as shown. 2. **Identify the relationship:** When two parallel lines are cut by a transversal, alternate interior angles are equal. 3. **Apply the rule:** The angle labeled 72° and the angle labeled y° are alternate interior angles. 4. **Set up the equation:** $$y = 72$$ 5. **Conclusion:** Therefore, the value of $y$ is 72 degrees.