Answer:
a 135° rotation.
Explanation:
As you can observe in the image attached, the preimage RST is a tringle "pointing" to the negaitve side of the vertical axis (taking point S as reference).
The transformed triangle R'S'T' is pointing to the diagonal of the first quadrant, with a 45°, approximately.
The rotation needed in such transformation would be 90° + 45° = 135°, becasue from -y to +x there're 90°, then we rotate 45° to reach the position of R'S'T'.
Therefore, the right asnwer is a 135° rotation.