Answer:
∠2 and ∠4 are the supplementary angle.
Step-by-step explanation:
Shelves of the bookcase are parallel and a transversal line is intersecting these points at two distinct points.
By the property,
Sum of two interior consecutive angles measure 180°.
From the figure attached,
∠2 and ∠4 are the interior consecutive angles.
Therefore, m∠2 + m∠4 = 180°
Which proves that shelves of the showcase are parallel.