3, 15, 27, 39,
describe the rule for the sequence.

The sequence is to add 12 to each new term.

Step-by-step explanation: The Best way to solve these type of questions is to quests and check. For example, one may notice 3 can be multiplied by 5 to get 15. However, 15 times 5 is 75, not 27, so the rule of multiply by 5 is not correct. Then, you may guess that the rule is to add some number to get the next. One may then notice that it is increasing by 12 each time.

1. 4

2. 2

3. 7

4. 12 because the square root to get a square root you have to know multiplication