Substitute in 2y everytime x appears in the circle equation:
Now use the quadratic formula to solve for y. You should get 2 answers. Substitute in y back into either equation to get the x co-ordinate and these are your points of intersection.
Find the point(s) of intersection. List all of the solutions.
x -2y = 0
(x-2)^2 + (y+2)^2 = 36
For the circle I think the radius is 6 and the center is (2,-2). From there I know that x = 2y but I get lost when substituting it in.