Решите системы уравнений : а)х+у=7 б) 2х-у=3 5х-3у=11 3х-у=5

Решите задачу:

$\left \{ {{x+y=7} \atop {5x-3y=11}} \right. \left \{ {{x=7-y} \atop {5(7-y)-3y=11}} \right. \left \{ {{x=7-y} \atop {y=3}} \right. \left \{ {{x=4} \atop {y=3}} \right.$
$5(7-y)-3y=11$
$35-5y-3y=11$
$8y=24$
$y=3$
$\left \{ {{2x-y=3} \atop {3x-y=5}} \right. \left \{ {{y=2x-3} \atop {y=3x-5}} \right. \left \{ {{3x-5=2x-3} \atop {y=3x-5}} \right. \left \{ {{x=8} \atop {y=19}} \right.$
$3x-5=2x-3$
$x=8$