[tex]\displaystyle\bf\\\left \{ {{2x + y = 4} \atop {x + y = 5 \: \: | \times ( - 1) }} \right. \\ \displaystyle\bf\\ + \left \{ {{2x + y = 4} \atop { - x - y = - 5 }} \right. \\ \\ 2x - x = 4 - 5 \\ x = - 1 \\ \\ - 1+ y = 5 \\ y = 5 + 1 \\ y = 6[/tex]

Ответ: ( - 1 ; 6 )