ПОМОГИТЕ СРОЧНО АЛГЕБРААА 8 КЛАССС Система линейных уравнений

Решите задачу:

$\left \{ {{2x-y=5} \atop {x-5,5y=15}} \right.\\\\\left \{ {{x=15+5,5y} \atop {2*(15+5,5y)-y=5}} \right. \\\\\left \{ {{x=15+5,5y} \atop {30+11y-y=5}} \right.\\\\\left \{ {{x=15+5,5y} \atop {10y=-25}} \right.\\\\\left \{ {{x=15+5,5y} \atop {y=-2,5}} \right.\\\\\left \{ {{x=15+5,5*(-2,5)} \atop {y=-2,5}} \right.\\\\\left \{ {{x=15-13,75} \atop {y=-2,5}} \right.\\\\\left \{ {{x=1,25} \atop {y=-2,5}} \right.$