Question

How do I do 90 counterclock wise rotations about the origin on points (-5,-5) , (0,-5) , (0,0)?

Answer 1

I don't know at what level you are working at, but if you
are into matrices, here is an excellent video that not only
develops the rotation matrix but actually uses a 90° rotation
as an example.
https://www.youtube.com/watch?v=OYuoPTRVzxY

If you don't know what a matrix is, why not just draw the points
on a graph and see where a 90° rotation puts you.
Btw, a positive rotation is counterclockwise, a concept that you
should remember from trig.

Answer 2

Just recall that such a rotation takes
(x,y) -> (-y,x)
So, (0,-5) -> (5,0)
and similarly for the other points

Answer 3

I'm not in trig yet. I'm going to 9th grade and will take geometry? (I think.. but thank you)