Divide each y-coordinate by its corresponding x-coordinate except for the point (0, 0). If every division gives you the same answer, it is proportional.
Table A:
2/(-2) = -1
3/(-1) = -3
Since -1 and -3 are different, this is not proportional.
Table B:
-3/(-1) = 3
3/1 = 3
6/2 = 3
All divisions give the same answer, 3. This is proportional.