F.3 coordinates

Since B is on the y -axis, the x-coordinate of B must be zero. Since ABCD is a parallelogram, when point C translate to point B, point D will translate to point A.
The x-coordinate of C is 8, when translate 8 units to the left will be point B, that means the x-coordinate of point D translate 8 units to the left will be point A, x-coordinate of point D is 12, therefore the x -coordinate of A will be 12 - 8 = 4. Therefore, the coordinate of A is (4,0).