from -2x-6y=4 we can express x as

x = (-6y - 4)/2 = -3y - 2

if we substitute for x = - 3y - 2 in 18y=6x-12 we get

18y=6(- 3y - 2) -12

18y = - 18 y - 12 - 12

36 y = - 24

y = - 24/36

y = - 2/3

x = - 3(-2/3) - 2 = 2 - 2 = 0

x = 0