as this is a parallelogram we get that
[tex]\begin{gathered} 7x-8=8x-17\rightarrow \\ 8x-7x=17-8 \\ x=9 \end{gathered}[/tex]having that x=9 we get that
[tex]\begin{gathered} 2\cdot(7\cdot9-8)+2\cdot(6y+17)=360 \\ 110+12y+34=360 \\ 12y=360-144 \\ 12y=216 \\ y=\frac{216}{12}=18 \end{gathered}[/tex]so we get that y=18
