All the given numbers are odd. The sum of any set of odd numbers is always odd if the quantity of the numbers in the sum is also odd.
All odd numbers can be expressed as 2n+1 where n is any number. For example, 1=2×0+1, 7=2×3+1, etc. In this example, the first n=0 and the second n=3.
If we have 5 odd numbers: 2n1+1, 2n2+1, 2n3+1, 2n4+1, 2n5+1, then add them together we get:
2(n1+n2+n3+n4+n5)+5 which can be written 2(n1+n2+n3+n4+n5+2)+1. We can represent the sum in parentheses by a single number N, so the sum is 2N+1 which is always an odd number. Therefore the sum can never be 30, which is even.