Question

Решите систему уравнений:
x+y=7
5x-7y=11

Answer 1

x+y=7
5x-7y=11

х=7-у
5(7-у)-7у=11
35-5у-7у=11
-12у=11-35
-12у=-24
у=2

х+2=7
х=7-2
х=5

Answer 2

$\left \{ {{x+y=7} \atop {5x-7y=11}} \right. \\ \\ \left \{ {{x=7-y} \atop {5(7-y)-7y=11}} \right. \\ \\ 35-5y-7y=11 \\ 35-12y=11 \\ 12y=24 \\ y=2 \\ x=5$

Ответ: $(5;2)$