При y = -6: -6 = 0.3x - 6 => 0.3x = 0 => x = 0.
При y = -3: -3 = 0.3x - 6 => 0.3x = 3 => x = 10.
При y = 0: 0 = 0.3x - 6 => 0.3x = 6 => x = 20.