Rotation Coordinate Notation About the Origin:
 90–degree counterclockwise: (x, y) → (-y, x)
 180–degree counterclockwise: (x, y) → (-x, -y)
 270–degree counterclockwise: (x, y) → (y, -x) 
Use this to help you.. 
Example - 
The vertices of a triangle are 
( 1 , 3 ) ( 3 , -4 ) , ( - 6 , -8 ) 
270 degrees , clockwise , rotated from origin ( x , y ) - ( y , -x ) 
The first vertice = ( 1 , 3 ) 
after rotation - ( 3 , - 1 ) 
The second vertice = ( 3 , -4 ) 
After rotation - ( -4 , -3 ) 
The third vertice = ( -6 , - 8 ) 
After rotation - ( -8 , 6 ) 
Hope my answer helps!