Final answer:
Segment DE is 15 units long and is parallel to segment AB.
Step-by-step explanation:
In triangle ABC, segment DE is a midsegment. The midsegment is a line segment connecting the midpoints of two sides of a triangle. It is parallel to and half the length of the third side of the triangle. In this case, segment DE is parallel to and half the length of segment AB. Since AB is 15 units, DE is also 15 units long.