Answer:
When two lines are cut by a transversal, if the alternate interior angles are equal in measure, then the lines are always parallel.
Explanation:
Given that when two lines are cut by a transversal, if the alternate interior angles are equal in measure,
then we have to tell lines are parallel or not.
Alternate interior angles are the angles formed on the inner side of two lines but on the opposite sides.
The above two angles are equal if two lines which cut by transversal are parallel.
Hence, when two lines are cut by a transversal, if the alternate interior angles are equal in measure, then the lines are always parallel.