Final answer:
Segment DC is twice the length of segment DE, so the length of segment DC is 30.
Step-by-step explanation:
The length of segment DC can be found using the properties of a centroid. In a triangle, the centroid divides each median into two segments, with the segment connecting the vertex to the centroid being twice as long as the segment connecting the centroid to the midpoint of the opposite side. Therefore, in this case, segment DE is half the length of segment DC. Since DE = 15, segment DC is twice that value, which is 30. Therefore, the length of segment DC is 30.