72 and 108 are same side interior angles. This is because they are on the same side of the transversal, and inside lines e and f.
It is the converse of same side interior angles theorem because converse means basically 180 degrees, and the converse of interior angle theorem means that if two lines are cut by a transversal, and two same side interior angles are supplementary, then the two lines are parallel.
72+108=180
The two angles are supplementary, because they equal 180 degrees.
