All you have to do is plug in the number for x, and find y. I will write this out as if in that chart you have shown.
x y = 9 - 3x y
_______________________________________
0 y = 9 - 3(0) 9
1 y = 9 - 3(1) 6
2 y = 9 - 3(2) 3
3 y = 9 - 3(3) 0
Hope that helps!!