Answer:
Explanation:
Every other one beginning with the first 3 adds 3 to the preceding number that has an odd position.
So the odd positions go up 3 6 9 12
And the next odd position is 15 which is the nineth term.
It's hard to tell what the even ones are doing. It could be anything just about. I'm guessing its a 9. So the tenth term is 9.
The sum of 9 and 15 = 24
If someone gives you a more consistent answer, take it.