Question: Below are two parallel lines with a third line intersecting them. $x^\circ$ $129^\circ$ Graph: two vertical parallel lines are crossed by a rising diagonal transversal; the $129^\circ$ angle is at the lower-left intersection on the right side of the left vertical line and below the transversal, and the $x^\circ$ angle is at the upper-right intersection on the left side of the right vertical line and above the transversal.

1. **State the problem:** We have two parallel lines cut by a transversal, creating angles $129^\circ$ and $x^\circ$ as described. 2. **Identify the relationship:** When two parallel lines are cut by a transversal, alternate interior angles are equal. 3. **Apply the rule:** The angle $129^\circ$ and the angle $x^\circ$ are alternate interior angles. 4. **Set up the equation:** $$x = 129$$ 5. **Conclusion:** Therefore, the value of $x$ is $129^\circ$. This is because alternate interior angles formed by a transversal crossing parallel lines are congruent.