One of the easiest ways to divide large numbers off the top of your head is to use the divisor (the number being divided by, not divided) to get yourself as close to the dividend as possible.
We know that 12 x 10 is 120, therefore if we double that we get to 240 (12 x 20), if we again do another set we get 360 (12 x 30), therefore we know that 3 is our first number in the problem!
Now, we subtract 396 - 360 = 36. How many more 12's can we make from 36?, 3 more! (12 x 3 = 36)
Therefore 396/12 = 33.
33
33
33
8.8
0.0028
33
9.4286
79.2
16.5
44
It is: 396/12 = 33
360