Решите систему уравнений методом подстановки: 4x-9y=3 x+3y=6

Решите задачу:

$\left \{ {{4x - 9y = 3} \atop {x+3y=6}} \right. \left \{ {{4x - 9y = 3} \atop {x=-3y+6}} \right. \left \{ {{4(-3y+6) - 9y = 3} \atop {x=-3y+6}} \right. \left \{ {{-21y + 21 = 0} \atop {x=-3y+6}} \right. \left \{ {{y=1} \atop {x=-3y+6}} \right. \left \{ {{y=1} \atop {x=3}} \right. ( 3 ; 1 )$