[tex]\displaystyle\bf\\\left \{ {{x - y = 3} \atop {x = - 2y }} \right. \\ \displaystyle\bf\\\left \{ {{ - 2y - y = 3} \atop {x = - 2y }} \right. \\ \\ - 3y = 3 \\ y = 3 \div ( - 3) \\ y = - 1 \\ \\ x = - 2 \times ( - 1) = 2 \\ \\ otvet \: \: \: (2; \: - 1) \\ x + y = 2 - 1 = 1[/tex]

Ответ: В)