6x + 3y = ?
3y = -6x + ?
y = -6/3x + ?/3
y = - 2x + ?/3
y = -2x + 4
no solutions means they are going to be parallel lines. That means they will have the same slope (-2) and different y int. So that blank space can be anything but 4 or 12...the reason 12 is also included is because 12/3 = 4.
answers are : -12, -4, 0