Question

\left \{ {{3(x+y)+1 = x+4y} \atop {7-2(x-y)=x-8y}} \right.

Answer 1

$\displaystyle \left \{ {{3(x+y)+1 = x+4y} \atop {7-2(x-y)=x-8y}} \right \\ \\ \\ \left \{ {{3x+3y+1=x+4y} \atop {7-2x+2y=x-8y}} \right. \\ \\ \\ \left \{ {{y=2x+1} \atop {10y+7=3x}} \right. \\ \\ \\ 10*(2x+1)+7-3x=0 \\ 20x+10+7-3x=0 \\ 17x=-17 \\ \\ x=-1 \\ y=2x+1=-1$

Ответ: {-1; -1}