Angle WVX and angle TVU are vertical angles, so they are congruent.
SV bisects angles TVX and USW. Therefore, angle SVX is congruent to angle SVT, and angle VSW is congruent to angle USV.
The measure of angle SVW is equal to the sum of the measures of angles SVX and WVX. The measure of angle SVU is equal to the sum of the measures of angles SVT and TVU.
Since angle WVX is congruent to angle TVU, and angle SVX is congruent to angle SVT, the measure of angle SVW can be written as the sum of the measures of angles SVT and TVU.
It has been established that the measure of angle SVU is equal to the sum of the measures of angles SVT and TVU, and the measure of angle SVW is also equal to the sum of the measures of angles SVT and TVU. Therefore, the measures of angles SVU and SVW are equal, so the angles are congruent.
Triangles SVW and SVU share side SV, angle VSW is congruent to angle USV, and angle SVW is congruent to angle SVU. Therefore, the triangles are congruent by the Angle-Side-Angle (ASA) postulate.
Because the two triangles are congruent, their corresponding parts are congruent (CPCTC). SU and SW are corresponding sides, so they are congruent.