1. **State the problem:** We need to find which angles are supplementary to angle $\angle 7$. Supplementary angles are two angles whose measures add up to $180^\circ$. 2. **Recall the rule:** When two lines intersect, adjacent angles are supplementary because they form a straight line. Also, angles on a straight line sum to $180^\circ$. 3. **Identify $\angle 7$'s supplementary angles:** - $\angle 7$ is at the upper-right intersection of two lines. - The angle adjacent to $\angle 7$ on the same straight line is $\angle 8$ (since they share a common side and form a straight line). - Therefore, $\angle 8$ is supplementary to $\angle 7$. 4. **Check other options:** - $\angle 3$ and $\angle 12$ are not adjacent to $\angle 7$ and do not form a straight line with it. - $\angle 2$ is also not adjacent or on the same straight line as $\angle 7$. 5. **Conclusion:** The only angle supplementary to $\angle 7$ from the given options is $\angle 8$. **Final answer:** $\angle 8$ is supplementary to $\angle 7$.