RU-SPB 2017 Problem 95

Given a scalene triangle $ABC$ with $\angle B=130^{\circ}$ . Let $H$ be the foot of altitude from $B$ . $D$ and $E$ are points on the sides $AB$ and $BC$ , respectively, such that $DH=EH$ and $ADEC$ is a cyclic quadrilateral. Find $\angle{DHE}$ .