In triangle QRT and triangle RTS , we have;
1.QR =SR (given)
2.RT bisects QS at T ( given )
3.T is the midpoint of QS (since RT is the bisector of QS i.e. QT=TS)
4.QT=TS (mid Point theorem)
5.TR=TR (common side)
6.triangle QRT congruent to triangle RTS (SAS criterion rule)
Hope this helps u....!!!