There is no mention if you can use sign or not and thus the only possible way to get this is as follows: (15 - 9) + (13 - 7) + (7 - 1) + (9 - 1) + (13 - 9). If you solve inside the brackets, you will get the following equation 6 + 6 + 6 + 8 + 4. Adding all these numbers will give you 30if the question would be-Q4: + + + + = 30This is what you have for the equation. The following are the numbers that you can use to fill in the brackets: 1, 3, 5, 7, 9, 11, 13 and 15. You can repeat the numbers if required. The resulting sum should be 30.