12:(9:3)

The mathematical expression 12:(9:3) can be interpreted in terms of division.

First, solve the inner part of the expression, which is 9:3:

9 divided by 3 equals 3.

Now we can substitute this result back into the original expression, transforming it to:

12:3

Now, compute this division:

12 divided by 3 equals 4.

Therefore, the answer to the expression 12:(9:3) is 4.