Choose which postulate/theorem proves the triangles congruent
M is the midpoint of line GL, line GK congruent to line LK
The postulate/theorem that proves the triangles congruent in this case is the Midpoint Theorem.
The Midpoint Theorem states that if a line segment is divided into two equal parts by a midpoint, then the two line segments on either side of the midpoint are congruent.
In this case, the given information states that M is the midpoint of line GL. Therefore, we can conclude that GK is congruent to LK based on the Midpoint Theorem.