If a transversal line is intersecting two given lines such that the sum of the measures of the angles on the same side of transversal is 180º, then the given two lines will be parallel to each other.
Here, ∠NML + ∠MLK = 180°
Hence,NM||LK
As quadrilateral KLMN has a pair of parallel lines, therefore, it is a trapezium.
