Question

____+____+____+=30 using 1,3,5,7,9,11,13,15

Answer 1

you cannot get 30 by adding any three numbers because all the above numbers are odd. And the addition of 3 odd numbers always give another odd number and hence 30 which is an even number cannot be achieved.

Answer 2

This is a trick question and you will not get any answer just by adding the numbers. I can give you one answer.

Do you know factorials?
1! = 1
2! = 2×1 = 2
3! = 3×2×1 = 6
4! = 4×3×2×1 = 24 and so on...

So the answer can be:

15 + 9 + 3! = 30
13 + 11 + 3! = 30