Those are all the problems that I can't figure out.
y=x (is this corect?)
S (-6,1)
T (-6,8)
U (-3,9)
V (-2,6)
and the prime coordinates I got were
S' (1,-6)
T' (8,-6)
U' (9,-3)
V (6,-2)
Suppose the original point's coordinates were (x, y). After reflecting across y = x, the new coordinates are (y, x).
So,
S (-6, 1) ==> S' (1, -6)
T (-6, 8) ==> T' (8, -6)
and so on.