easy explanation pls

Notice  that the   difference in the x coordinates of the two points  =  14 - 6  = 8

So......(1/4)  of this = 2

Adding this to the x coordinate of (6,4) , we have the x coordinate of D  = 6+2 = 8

And  the   difference in the y coordinates  =  12 - 4  = 8

So......(1/4)  of this = 2

Adding this to the y coordinate of (6,4) , we have the y coordinate of D  = 4+2 = 6

So......D  =  (8, 6)