The SAS Theorem (Side-Angle-Side) states that two triangles are equal if two sides and the angle between those two sides are equal.
In the given figure, the angle should be between the two sides which is represented by the right angle. Since both triangles have XV as the first side, the second side should be the one adjacent to the right angle which is WV and KX.
Therefore, the additional information that is required to know that the triangles are congruent is:
