Answer:
-12, -4,0, 4
Explanation:


We need to find out the unknown number
When the system of equations have no solution only the lines are parallel.
the lines are parallel then the slopes are equal and y intercept are different
, slope is the coefficient of x. slope = -2

Move 6x to the other side and Solve the equation for y
, divide both sides by 3
. slopes are same . y intercept can be any number.
not equal to 4
So the value of 'a' not equal to 12
Hence y intercept are all numbers except 12