There's no information about the relation between the points so I'm guessing that R, S and T are in a line and S is the midpoint of RT. Let R be the point (x,y), then the coordinates of S are the average of the coordinates of R and T.
Therefore -4=½(x-7) and -6=½(y-3),
-8=x-7, x=-1; -12=y-3, y=-9, so R is (-1,-9).