Since the two marked angles are congruent, according to the Corresponding Angles Theorem, the segment in the middle of this triangle is parallel to one of its sides.
If a segment parallel to one of the sides of a triangle is drawn between the other sides, the segment divides the other two sides proportionally.
Let's write a proportion using the expressions for the lengths of the segments.
13x+2/23x-4 = 5y/73y+8
Since we know that two segments on the left side are congruent, we know that two segments on the right side are also congruent. Let's solve the equation 5y = 73y+8 to find y.
