Respuesta :

[tex]\begin{gathered} \angle BDR=m\angle BDJ+m\angle JDR \\ \angle BDR=7y+2+2y+7 \\ \angle BDR=9y+9 \\ 90-9=9y \\ 81=9y \\ y=\frac{81}{9} \\ y=9 \end{gathered}[/tex]