The postulate that proves the triangles in the figure congruent is the SAS
What SAS postulate?
The SAS Postulate is one of the congruence postulates used in geometry to prove that two triangles are congruent.
The SAS Postulate states that if two sides and the included angle of one triangle are congruent to the corresponding two sides and included angle of another triangle, then the two triangles are congruent.
The mid point mentioned helped to shoe that the sides are congruent by midpoint theorem. The figure is already showing the congruent angles