## Geometry: Common Core (15th Edition)

$DE = 7.5$
The diagonals of a parallelogram bisect one another; therefore, if the entire diagonal is $15$, then each bisected segment is half of this length: $DE = \frac{1}{2}(15)$ Multiply to simplify: $DE = \frac{15}{2}$ Divide to solve: $DE = 7.5$