Question

X + y = 50} x - y = 0

Answer 1

$\left \{ {{x+y=50} \atop {x-y=0}} \right. \\\\ x-y=0\to x=y\\\\\\ x+y=50\to y+y=50 \to 2y=50 \to y= \frac{50}{2} \to y=25\\\\\\ x=y\to x=25\\\\\\\\ S= \left \{ 25;25 \left \}$