Is n divisible by 12?
1. n/6 is an integer.
2. n/4 is an integer.

[spoiler]from 1) N can be 6,12,18,24,30,36,42 ... (Insufficient)

from 2) N can be 4,8,12,16,20,24 ... (Insufficient)

From 1 and 2, N can be 12,24, ... (Sufficient)[/spoiler]