Answer:
every number you can think of
Explanation:
6x - 3y = -6
=> 3(2x - y) = -6
=> 2x - y = -2
And you see there's a problem here. The question doesn't have enough information because x and y can be every numbers.
Take an example, x can be 200 and y can be 402 or x can be 5 and y can be 12.
Rewrite or check the question again so I can solve this :)