Ребят хелп 2 уравнения , срочно!!

$1) \left \{ {{3x+y=7} \atop {9x-4y=-7}} \right. \\ \left \{ {{y=7-3x} \atop {9x-4\cdot (7-3x)=-7}} \right. \\ \left \{ {{y=7-3x} \atop {9x-28+12x=-7}} \right. \\ \left \{ {{y=7-3x} \atop {9x+12x=-7+28}} \right. \\ \left \{ {{y=7-3x} \atop {21x=21}} \right. \\ \left \{ {{y=7-3\cdot1} \atop {x=1}} \right. \\ \left \{ {{y=4} \atop {x=1}} \right. \\$
Ответ. (1;4)
$2) \left \{ {{x-3y=6} \atop {2y-5x=-4}} \right. \\ \left \{ {x=3y+6} \atop {2y-5\cdot (3y+6)=-4}} \right. \\ \left \{ {{x=3y+6 \atop {2y-15y-30=-4}} \right. \\ \left \{ {{x=3y+6} \atop {-13y=26}} \right. \\ \left \{ {{x=3y+6} \atop {y=-2}} \right. \\ \left \{ {{x=3\cdot(-2)+6} \atop {y=-2}} \right. \\ \left \{ {{x=0} \atop {y=-2}} \right. \\$
Ответ. (0; -2)