Question

resolva o sistema {x-y=12 x+y=20

Answer 1

$\left \{ {{x-y=12} \atop {x+y=20}} \right. \\\\\\ x-y=12\to x=y+12\\\\\\ x+y=20\to y+12+y=20\to 2y=20-12\to 2y=8\to y= \frac{8}{2} \to \\\\ y=4\\\\\\ x=y+12\to x=4+12\to x=16\\\\\\\\ S=(16;4)$