Ответ:

1. x=12; y=-21

2. x=1; y=-1

Объяснение:

1)

[tex]-\left \{ {{4x+3y=-15} \atop {5x+3y=-3}} \right.[/tex]  [tex]\left \{ {{x=12} \atop {5*12+3y=-3}} \right.[/tex]  [tex]\left \{ {{x=12} \atop {60+3y=-3}} \right.[/tex] [tex]\left \{ {{x=12} \atop {3y=-63}} \right.[/tex] [tex]\left \{ {{x=12} \atop {y=-21}} \right.[/tex]

        x=12

2)

[tex]+\left \{ {{5x-7y=12} \atop {8x+7y=1}} \right.[/tex]  [tex]\left \{ {{x=1} \atop {8*1+7y=1}} \right.[/tex]  [tex]\left \{ {{x=1} \atop {7y=-7}} \right.[/tex] [tex]\left \{ {{x=1} \atop {y=-1}} \right.[/tex]

    13x=13

     x=1