Answer:
Lines are parallel if the sum of external angles of same side is 180°.
Step-by-step explanation:
Let one of the external angle is α°.
and other external angle is β° which is equal to α°/11. (∵ Given on is 11 times smaller than the other.)
Also β° = 1/6 of the right angle = (1/6)×90° = 15°.
β° = α°/11 , ⇒ α° = 11×β° = 11×15° = 165°.
α°+β° = 165° + 15° = 180°.
Here, sum of the two external angles = 180° ⇔ the given lines are parallel.
