{ 3- ( x-2y) - 4y= 18
{ 2x -3y +3=2 (3x-y}

раскрываем скобки
{3-x+2y-4y=18
{2x-3y+3=6x-2y

{-x-2y=15
{-4x-y=-3

{x=-15-2y
{x=(3-y)/4

15-2y=(3-y)/4
60-8y=3-y
60-3=-y+8y
57=7y
y=57/7=

x=-15-2y=-15-114/7= (-105-114)/7=-219/7 =-31 2/7