Чему равно сумма Х+У

$\displaystyle \left \{ {{\bigg(\cfrac{1}{5} \bigg)^{2y-x}=25} \atop {3^{y-2x}=\cfrac{1}{27}}} \right. \ \ \Rightarrow \ \ \left \{ {{5^{-(2y-x)}=5^2} \atop {3^{y-2x}=\cfrac{1}{3^3}}} \right. \ \ \Rightarrow \ \ \left \{ {{5^{-2y+x}=5^2} \atop {3^{y-2x}=3^{-3}}} \right. \ \ \Rightarrow \ \ \\\\\\\\ \ \ \Rightarrow \ \ \left \{ {{-2y+x=2} \atop {y-2x=-3} \ | \cdot 2} \right. \ \ \Rightarrow \ \ \left \{ {{-2y+x=2} \atop {2y-4x=-6}} \right.$