In the adjacent figure, a line n falls on lines l and m such that the sum of the interior angles 1 and 2 is less than 180°, then what can you say about lines l and m.

By Euclid’s Postulate 5,

We know that if a straight line falling on two straight lines makes the interior angles on the same side of it taken together less than two right angles, then the two straight lines, if produced indefinitely, meet on that side on which the sum of angles is less than two right angles.

Given, a line n falls on lines l and m such that the sum of the interior angles 1 and 2 < 180° on the right side of line n.

So, the lines l and m will eventually intersect on the right side of line n.