hElp, I don't understand at all.

Question

3. Complete the table and state the rule.
0 | 0
| 3
2 |
3 | 9
|
5 | 15
6 |

Please help. :'v

Answer 1

Note that
3*0 = 0
3*3 = 9
3*5 = 15
The rest should be easy to fill in

Answer 2

Thank you, looking at that I realize I'm very ... stupid.
0 | 0
1| 3
2 | 6
3 | 9
4 | 12
5 | 15
6 | 18

Answer 3

What's the rule?