Question

In triangle QRS, QR is congruent to SR and RT bisects QS. What justification can you give for QRT congruent to SRT and give the Triangle Congruence Postulate that supports your reason.
Answers:

Midpoint Theorem, SSS

Given, SSS

Definition of a segment bisector; SSS

Definition of an isosceles triangle, SAS,

Answer 1

The answer is Definition of a segment bisector; SSS.
Explanation:

Since RT bisects QS, we have QT congruent to ST. 
 By SSS, we have triangle QRT congruent to triangle SRT
so, since QT is congruent to ST, RT is congruent to RT, and QR is congruent to SR.
All these sides are congruent to each other that gives the proof of "SSS(SIDE, SIDE, SIDE)" 

Answer 2

Since RT bisects QS, we have QT congruent to ST. Bisect means it cuts QS in half. The we have RT congruent to RT since it is the same. By SSS, we have triangle QRT congruent to triangle SRT since QT is congruent to ST, RT is congruent to RT, and QR is congruent to SR. Each side is congruent to its respective side in the other triangle and that is SSS (side, side, side).