Answer:
Addition (+)
Explanation:
If we were to take the problem and form an expression, it would look like this:
3 times a number (3 ×?) decreased by 2 (- 2) divided by 6 (÷ 6)
Putting it all together it forms:
The four operations are addition, subtraction, multiplication and division.
We can see the multiplication, subtraction, and division, but not addition.
Therefore, the operation that is missing is Addition.