Question

Найти неизвестные х+у=23 и 2х+3у=61

Answer 1

$\displaystyle \tt \left \{ {{x+y=23} \atop {2x+3y=61}} \right. \to \left \{ {{x=23-y} \atop {2x+3y=61}} \right. \\\\\displaystyle \tt 2(23-y)+3y=61\\\displaystyle \tt 46-2y+3y=61\\\displaystyle \tt y=61-46\\\displaystyle \tt \bold{y=15}\\\\\displaystyle \tt x=23-15\\\displaystyle \tt \bold{x=8}\\\\\displaystyle \tt (x; \: y)=(8; \: 15)$

Ответ: $\displaystyle \tt (x; \: y)=(8; \: 15)$