Explanation:
the midpoint has actually the coordinates that are halfway between the x coordinates and halfway between the y coordinates.
so, whatever we have to subtract from T to get to the midpoint, we have to subtract again to get to S.
for x we get
10 - 5 = 5
so, we need to subtract another 5 for the x coordinate of S.
that is then 5 - 5 = 0.
for y we get
19 - 29 = -10
so, we need to subtract another 29 for the y coordinate of S.
that is then -10 - 29 = -39
S = (0, -39)