Question: 21. In the figure shown, PR bisects $\angle QPR$, $m\angle QPR = 64^\circ$, and $m\angle RPS = (2x + 10)^\circ$. What is the value of $x$?
1. **State the problem:** We are given that $PR$ bisects $\angle QPR$, the measure of $\angle QPR$ is $64^\circ$, and the measure of $\angle RPS$ is $(2x + 10)^\circ$. We need to find the value of $x$.
2. **Understand the angle bisector:** Since $PR$ bisects $\angle QPR$, it divides $\angle QPR$ into two equal angles. Therefore,
$$m\angle QPR = 2 \times m\angle RPS$$
3. **Set up the equation:** Given $m\angle QPR = 64^\circ$ and $m\angle RPS = (2x + 10)^\circ$, we write
$$64 = 2(2x + 10)$$
4. **Simplify the equation:**
$$64 = 4x + 20$$
5. **Isolate $x$:**
$$64 - 20 = 4x$$
$$44 = 4x$$
6. **Divide both sides by 4:**
$$\cancel{4}x = \frac{44}{\cancel{4}}$$
$$x = 11$$
7. **Conclusion:** The value of $x$ is $11$.
**Final answer:** $x = 11$ (Option A)