Answer:
Given : S â•‘ T,
We have to prove that : ∠3 and ∠5 are supplementary
Proof :
Thus, the column proof is as follow,
    Statement                    Reason
1. Â S â•‘ T Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 1. Given
2. ∠1 and ∠3 are supplementary    2. exterior sides in opposite ray
3. m∠1 + m∠3 = 180°              3. Definition of supplementary
4. m∠1 = m∠5                    4. if lines are ║, cor. angles are equal
5. m∠5 + m∠3 = 180°              5. Substitution
Hence, ∠3 and ∠5 are supplementary.
Note : Since, if the exterior sides are opposite rays, then they always form a straight line.