? + ? + ? = 30. Fill the boxes using (1,3,5,7,9,11,13,15) you can repeat the numbers.

Take care of these following properties:

The sum of two odd numbers is even

Sum of two even numbers is even

Sum of odd and even number is odd

The number required is even, but we have all odd numbers to place in the boxes. So, we have to create an even number at any one boxes. For box 2 we are taking 13 and for box 3 taking 11. So 13 + 11 = 24 is achieved. Now we are left with 6 more. So, in first box number = [7–1]

Hence the problem is solved.

multiple answers are possible in a similar manner.