Lúc nãy chị ấn nhầm nhé.
$\left \{ {{3(x+y)+9=2(x-y) } \atop {2(x+y)=2(x-y)-11}} \right.$
<=> $\left \{ {{3x + 3y + 9 =2x - 2y} \atop {2x + 2y = 2x - 2y - 11}} \right.$
<=> $\left \{ {{3x + 3y -2x + 2y=-9} \atop {2x + 2y -2x + 2y =- 11}} \right.$
<=> $\left \{ {{x+5y=-9} \atop {4y=-11}} \right.$
<=> $\left \{ {{x=\frac{19}{4}} \atop {y=-\frac{11}{4} }} \right.$
Vậy x = $\frac{19}{4}$
y = -$\frac{11}{4}$
