Let's break down the questions in the image one by one.

Question 9:

Problem: If lines $m$ and $n$ are parallel, what must be true about $\angle A$?

We are given that the lines $m$ and $n$ are parallel and $\angle A$ is associated with a transversal cutting through the two lines, creating angles with a given value of 50°.

Solution: When two parallel lines are cut by a transversal, alternate interior angles are congruent. Also, corresponding angles on the same side of the transversal are supplementary. Based on the diagram, $\angle A$ is the alternate interior angle, so: $m \angle A = 180^\circ - 50^\circ = 130^\circ.$ Thus, none of the options match perfectly, but perhaps we need to check angles based on corresponding angles.

Question 10:

Problem: Parallel lines $m$ and $n$ are intersected by a transversal $t$, and $\angle 1$ measures 112°. We need to identify which other angles also measure 112°.

Solution:

• $\angle 1$ and $\angle 5$ are corresponding angles, so $m \angle 5 = 112^\circ$.
• $\angle 1$ and $\angle 3$ are alternate interior angles, so $m \angle 3 = 112^\circ$.
• $\angle 1$ and $\angle 6$ are also corresponding angles on the same side of the transversal, so $m \angle 6 = 112^\circ$.

Thus, the angles measuring 112° are $\angle 3$, $\angle 5$, and $\angle 6$.

Question 11:

Problem: We are given two angles $(6x + 27)^\circ$ and $(12x - 9)^\circ$, and we need to solve for $x$ and the measure of $\angle BCD$.

Solution: The two angles are vertically opposite, which means they are equal: $6x + 27 = 12x - 9.$ Solving for $x$: $6x - 12x = -9 - 27,$ $-6x = -36,$ $x = 6.$

Now, substitute $x = 6$ into either angle expression: $6(6) + 27 = 36 + 27 = 63^\circ.$ Thus, $m \angle BCD = 63^\circ$.

Question 12:

Problem: Which of the following is defined as a part of a line that is bounded by two endpoints?

Solution: The correct definition of a part of a line bounded by two endpoints is a segment. Thus, the answer is D: segment.

Would you like more details on any of these problems, or do you have any questions?

Here are five additional related questions to further your understanding:

1. What are the properties of corresponding angles when two parallel lines are cut by a transversal?
2. How do alternate interior angles relate when two lines are parallel?
3. What is the definition of a transversal, and how does it affect angles formed by parallel lines?
4. Can vertical angles ever be supplementary? Why or why not?
5. How can the concept of congruent angles be applied to other types of geometric figures?

Tip: When solving for angles with parallel lines, remember that corresponding, alternate interior, and alternate exterior angles are equal.