Question

Решите систему уравнений

{х-2у=0
{10х+у=42

Answer 1

$\left \{ {{x-2y=0} \atop {10x+y=42}} \right.$
$\left \{ {{10x-20y=0} \atop {10x+y=42}} \right.$
$-21y=-42$
$y=-42:(-21)$
$y=2$
$10x+2=42$
$10x=42-2$
$10x=40$
$x=40:10$
$x=4$
Ответ: (4 ; 2)