Решите систему методом подстановки х+ 3у=9 и 3х-у= 7

$\left \{ {{x+3y=9} \atop {3x-y=7}} \right. ; \left \{ {{x=9-3y} \atop {3x-y=7}} \right. ; \left \{ {{x=9-3y} \atop {3*(9-3y)-y=7}} \right. ; \left \{ {{x=9-3y} \atop {27-9y-y=7}} \right. ; \\ \left \{ {{x=9-3y} \atop {-10y=-20}} \right. ; \left \{ {{x=9-3y} \atop {y=2}} \right. ; \left \{ {{x=9-3*2} \atop {y=2}} \right. ; \left \{ {{x=3} \atop {y=2}} \right.$
Ответ: (3;2)