Answer:
U is the midpoint of SR and QT (given).
QU is congruent to UT (definition of midpoint).
SU is congruent to UR (definition of midpoint).
Angle QUS is congruent to angle TUR (vertical angles are congruent).
∆QUS is congruent to ∆TUR (SAS).
QS is congruent to TR (CPCTC).