I don't see any choices so I am going to give you what I think the answer would be. The rule would be 3x. That would be you could plug any number in and they would give you the sequence. Example: x = 1 x times 3 = 3. We could even find future things like: x = 10 x times 10 = 30. If we were doing it based on the algebraic expression it would be "multiplication" because we are multiplying. Hope this helped. :)
