Answer:
Step-by-step explanation:
The transformations you want are ...
Taken together, these make the transformation ...
(x, y) ⇒ (-y+6, -x-1)
So, your points become ...
A(0, 0) ⇒ A'(6, -1)
B(8, 1) ⇒ B'(5, -9)
C(5, 5) ⇒ C'(1, -6)
___
The attachment shows the original triangle in red and the progression to the final triangle in blue.