If the lines X + 2y-1 = 0 and y = KX are parallel to each other, then the value of the real number k is______ .

If the lines X + 2y-1 = 0 and y = KX are parallel to each other, then the value of the real number k is______ .

∵ the lines X + 2y-1 = 0 and y = KX are parallel to each other ∵ the slopes of the two lines are equal, k = - 12, so the answer is: - 12