Решите систему уравнений x/3=-y/4 x+y=5

$\left \{ {{ \frac{x}{3}=- \frac{y}{4} } \atop {x+y=5}} \right.$
$\left \{ {{ \frac{x}{3}=- \frac{y}{4} } \atop {x=5-y}} \right.$
$\left \{ {{ \frac{5-y}{3}=- \frac{y}{4} } \atop {x=5-y}} \right.$
$\left \{ {{ \frac{5-y}{3}+\frac{y}{4}=0 } \atop {x=5-y}} \right.$
$\left \{ {{ \frac{4(5-y)}{12}+\frac{3y}{12}=0 } \atop {x=5-y}} \right.$
$\left \{ {{ 4(5-y)+3y=0 } \atop {x=5-y}} \right.$
$\left \{ {{20-4y+3y=0 } \atop {x=5-y}} \right.$
$\left \{ {{20-y=0 } \atop {x=5-y}} \right.$
$\left \{ {{y=20 } \atop {x=5-y}} \right.$
$\left \{ {{y=20 } \atop {x=5-20}} \right.$
$\left \{ {{y=20 } \atop {x=-15}} \right.$
ответ: (-15; 20)