Geometry

Question Analysis:
This question focuses on the properties of triangles sharing sides.
The main idea is to use the given side - length information to determine triangle congruence and related angle equalities.

Key Concept Explanation:
- SSS (Side - Side - Side) congruence criterion: If three sides of one triangle are equal to three sides of another triangle, the triangles are congruent.
- For congruent triangles, corresponding angles are equal.

Step - by - Step Solution:
1. Given , , and is common to both and