(1) Rotate ACDE 270° clockwise around
the origin

Answer:
C=(1,3)
D=(3,3)
E=(1,1)
Step-by-step explanation:
Since you're rotating 270° clockwise around the origin, you're actually rotating 90° counter-clockwise. So, this means that the transformed version of (x,y) is (y,-x).
So:
C (3,-1) → (1,3)
D (3,-3) → (3,3)
E (1,-1) → (1,1)