Since 2 and 4 are mathematical sequences, can I suggest:
1. Odds decrease by 2, evens decrease by 3, hence 2
3. Odds total 10,12, 14 making last one 7
5. 1st and 5th total 10,2nd and 6th 11, 3rd and 7th 12 so last number 7
6. 1st even pair total 13 2nd reduces by 2, 1st odd pair total 15, 2nd reduces by 3, so last number 9