Look at this series: 7, 10, 8, 11, 9, 12, ... What number should come next?

Answer: 10.

Explanation:

• Split the sequence into two interleaved subsequences.

• Odd-position terms (1st, 3rd, 5th, ...): 7, 8, 9, ... (increasing by 1).

• Even-position terms (2nd, 4th, 6th, ...): 10, 11, 12, ... (increasing by 1).

• The given sequence ends with 9 (5th term) and 12 (6th term); the next term is the next odd-position term after 9, which is 10.

Therefore the next number in the series is 10.