[tex]\displaystyle\bf\\\left \{ {{ - 3x + 4y = - 9 \: \: | \times 4} \atop {4x + 3y = - 13 \: \: | \times 3}} \right. \\ \displaystyle\bf\\ + \left \{ {{ - 12x + 16y = - 36} \atop {12x + 9y = - 39 }} \right. \\ \\ 16y + 9y = - 39 - 36 \\ 25y = - 75 \\ y = - 75 \div 25 \\ y = - 3 \\ \\ 4x + 3 \times ( - 3) = - 13 \\ 4x - 9 = - 13 \\ 4x = - 13 + 9 \\ 4x = - 4 \\ x = - 4 \div 4 \\ x = - 1[/tex]

Ответ: ( - 1 ; - 3 )