Question

What additional information is needed to prove the triangles are congruent by the SAS postulate

Answer 1

SAS stands for sida-angle-side
this means that at least 2 sides must be congruent and 1 angle must be too

Answer 2

Two triangles are congruent if their corresponding sides are equal in length, and their corresponding angles are equal in measure.

To prove that triangles are congruent by the SAS (Side Angle Side) postulate you need two equal corresponding sides and the two angles between them be congruent too.