I think you meant to say the sum of three CONSECUTIVE odd numbers. You can never get an even number by adding three odd numbers. Two odds is an even but three odds is still an odd.
What is meant by three consecutive odd numbers is the following:
X (the first number), x + 2 (the second number), x + 4 (the third number)
x + (x + 2) + (x + 4) = 30
x + x + 2 + x + 4 = 30
3x + 6 = 30
3x = 24
x = 8
So now that we have the x-value, we can determine what the numbers are:
x = 8
x + 2 = 10
and x + 4 = 12