Explanation:

- In the set (15, 135, 6): Multiply 15 by 9 to get 135, then subtract 9 to get 6.

- In the set (12, 84, 5): Multiply 12 by 7 to get 84, then subtract 7 to get 5.

Let's examine the options:

- Option 1: (21, 315, 6)

- Multiply 21 by 15 to get 315, then subtract 15 to get 6.

- Option 2: (9, 89, 3)

- Multiply 9 by 10 to get 90, then subtract 10 to get 80, which doesn't fit.

- Option 3: (24, 145, 18)

- This set doesn't fit as the pattern doesn't work with these numbers.

- Option 4: (17, 165, 7)

- Multiply 17 by 9 to get 153, which doesn't give 165, thus doesn't fit the pattern.