When a transverse line intersects three parallel lines, eight angles are formed. These angles can be classified into two groups: corresponding angles and alternate interior angles.
Corresponding angles are congruent, meaning they have the same measure. There are four pairs of corresponding angles formed by the transverse and the parallel lines.
Alternate interior angles are also congruent. There are four pairs of alternate interior angles formed by the transverse and the parallel lines.
So in total, there are 8 angles formed, and all corresponding angles and alternate interior angles are congruent to each other.