1. Given: ∠TWX and ∠UTW are supplementary.
2. Definition of Supplementary Angles: Supplementary angles add up to 180 degrees.
3. ∠TWX + ∠UTW = 180 degrees. (From statement 1 and definition of supplementary angles)
4. ∠RTU + ∠UTW = 180 degrees. (Because ∠TWX and ∠UTW are supplementary)
5. Substitution Property of Equality: If two quantities are equal to a third quantity, then they are equal to each other.
Thus, ∠TWX + ∠UTW = ∠RTU + ∠UTW.
6. Subtract ∠UTW from both sides: ∠TWX = ∠RTU.
7. If two lines are cut by a transversal and corresponding angles are congruent, then the lines are parallel.
Thus, SU || VX. (Based on the fact that ∠TWX = ∠RTU and the definition of parallel lines)