Answer:
1. (x,y)→(y,-x)
2. (x,y)→(-y,x)
3. (x,y)→(-x,-y)
Explanation:
1. Rotation 90° clockwise (or 270° counterclockwise) about the origin changes x into y and y into -x, so it has the rule
(x,y)→(y,-x)
2. Rotation 90° counterclockwise (or 270° clockwise) about the origin changes x into -y and y into x, so it has the rule
(x,y)→(-y,x)
3. Rotation 180° clockwise about the origin changes x into y and y into -x, so it has the rule
(x,y)→(-x,-y)
Here you can apply rotation by 90° clockwise twice, so
(x,y)→(-y,x)→(-x,-y)