A pair of parallel lines is cut by a transversal, as shown in the figure:

A pair of parallel lines is cut by a transversal. The interior angle made on the left by the intersection of the upper parallel line and the transversal is labeled as x. The interior angle made on the right by the intersection of the lower parallel line and the transversal is labeled as y.

Which of the following best represents the relationship between angles x and y?

x = y
x = 180 degrees − y
y = 180 degrees − x
x = 2y

The best representation of the relationship between angles x and y is "x = y." This is because when a transversal cuts a pair of parallel lines, the corresponding angles are congruent. In this case, x and y are corresponding angles, so they are equal to each other.