jmc

Let $w=2x+z$. The equations become $$\begin{array}{rl}2w-y& =7,\\ 3w+3y& =5.\end{array}$$ Subtracting twice the second equation from three times the first equation, $$6w-3y-6w-6y=21-10\Rightarrow -9y=11.$$ Thus $y=\boxed{-\frac{11}{9}}$.