The vertices of the given figure are
A(1, -1), B(5.-6), and C(1, - 6).
For a 90 counterclockwise about the origin, a coordinate, (x, y) would be (- y, x)
This means that after the 90 degrees rotation,
coordinate A would be (- - 1, 1) = (1, 1)
Coordinate B would be (- - 6, 5) = (6, 5)
Coordinate C would be (- - 6, 1) = (6, 1)