So i know how to reflect over line y=-x but how would i do it over line y=-x+6. an example would be and a rule for more problems of this kind.

To reflect in the line y = -x + 6, we translate everything down 6 first. This will make it seem like we are reflecting in the line y = -x
                                 (x,y) → (x, y-6)
Then, to reflect in the line y = -x, we switch the x- and y-coordinates and then make them negative
                                 (x,y) → (-(y-6), -x)     
Then we move everything back up again
                                 (x,y) → (-(y-6), -x + 6)          
I will present to you an example. Reflect the point (-4, 8) in the line y = -x + 6.
                                 (-4,8) → (-(8-6), -(-4) + 6) → (-2, 10)
You should graph this out to confirm with the reflection line.