Puzzle ZDTU 

Workings

Hint
Does the number of adults and children matter?

Answer
3,672.

Reasoning
The actual number of adults and children doesn't matter.

For example, if all of the people were adults, then half of them (306) would be given 12 sweets:

  306 x 12 = 3672

For example, if all of the people were children, then three quarters of them (459) would be given 8 sweets:

  459 x  8 = 3672

For example, if there were 512 adults (so 256 would get 12 sweets = 3072) and 100 children (so 75 would get 8 sweets = 600):

  256 x 12 + 75 x 8 = 3672

As you can see, we can change the numbers of adults and children, and it doesn't change the answer.

The reason for this lies in the fact that
   ¹⁄₂ adults x 12 sweets
and
   ³⁄₄ children x 8 sweets
both equal 6 sweets.