x - 4 = -8 add 4 to both sides
x = -4
Put the value of x to the first equation 3x - 12y = -6:
3(-4) - 12y = -6
-12 - 12y = -6 add 12 to both sides
-12y = 6 divide both sides by (-12)
y = - 0.5
Answer: x = -4 and y = -0.5
New question:
x - 4y = -8 add 4y to both sides
x = 4y - 8
Substitute it to the first equation:
3(4y - 8) - 12y = -6 use distributive property
(3)(4y) + (3)(-8) - 12y = -6
12y - 24 - 12y = -6
-24 = -6 FALSE
Answer: No solution.