Помогите срочно...................................

Решите задачу:

$\left \{ {{2x+3y=-11} \atop {2x-3y=7}} \right. |+ \left \{ {{4x=-4} \atop {2x-3y=7}} \right. \left \{ {{x=-1} \atop {-3y=9}} \right. \left \{ {{x=-1} \atop {y=-3}} \right.$

$\left \{ {{4x-y=27} \atop {4x+y=29}} \right. |+ \left \{ {{4x-y=27} \atop {8x=56}} \right. \left \{ {{-y=-1} \atop {x=7}} \right. \left \{ {{y=1} \atop {x=7}} \right.$

$\left \{ {{-x-9y=33} \atop {9y-x=-21}} \right. |+ \left \{ {{x+9y=-33} \atop {-2x=12}} \right. = \left \{ {{9y=-27} \atop {x=-6}} \right. \left \{ {{y=-3} \atop {x=-6}} \right.$

$\left \{ {{9y-8x=89} \atop {-9y-8x=-73}} \right.|+ \left \{ {{-16x=16} \atop {9y+8x=73}} \right. \left \{ {{x=-1} \atop {9y=81}} \right. \left \{ {{x=-1} \atop {y=9}} \right.$