Because the two lines are parallel, and there is a transversal line that splits the 72 degrees and x, you know that x + 72 = 180 (you also can just see that it is a straight line). Solve this by doing 180 - 72 and getting x = 108 degrees
[tex]x° = 180° - 2 \times 72° = 180° - 144° = 36°[/tex]
