Dilation centered at the origin with a scale factor of k transforms the point (x, y) into (kx, ky).
Applying this rule to the trapezoid given we get:
Q(0, 0) → (1/2*0, 1/2*0) → Q'(0,0)
R(0, 6) → (1/2*0, 1/2*6) → R'(0, 3)
S(6, 6) → (1/2*6, 1/2*6) → S'(3, 3)
T(8, 0) → (1/2*8, 1/2*0) → T'(4, 0)