Since we are dividing the line segment NM in a ratio of 1:3, ND is 1/4 of the length of NM and DM is 3/4 of the length of NM.
From N to M, the x coordinates decrease by 12, from 8 to -4.
x-coordinate of D = 8 - (1/4)(12) = 5
From N to M, the y-coordinates increase by 12, from -1 to 11.
y-coordinate of D = -1 + (1/4)(12) = 2
So, D = (5,2)