Final answer:
The common side of the congruent triangles UYX and VYW is side UY.
Step-by-step explanation:
The common side of congruent triangles UYX and VYW is side UY.
When two triangles are congruent, it means that they have the same shape and size. This means that all corresponding sides and angles are equal. In the given question, triangles UYX and VYW are congruent, so their corresponding sides are equal.
Since the question asks for the common side, the correct answer is side UY.