Решить систему уравнений x+y=7 5x-7y=11

$\left \{ {{x+y=7} \atop {5x-7y=11}} \right.$

$\left \{ {{x=7-y} \atop {5(7-y)-7y=11}} \right.$

$5(7-y)-7y=11$

$35-5y-7y=11$

$35-12y=11$

$12y=35-11$

$12y=24$

$y=24:12$

$y=2$

$x=7-y=7-2=5$

$\left \{ {{x=5} \atop {y=2}} \right.$

Проверка:

$\left \{ {{5+2=7} \atop {5\cdot5-7\cdot2=11}} \right.$

$\left \{ {{7=7} \atop {25-14=11}} \right.$

$\left \{ {{7=7} \atop {11=11}} \right.$