Let's divide 399190 by 12
Let's see how many times 12 fits into 399190.

Step 1:
12 can be fit into 3 0 times, resulting in a remainder of 3.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Deduct 0 from 3 and we're left with 3.
Append the next digit (9) from the dividend to 3 and continue with: 39 / 12

Step 2:
12 goes into 39 3 times with a remainder of 3.
Use 3 as the next digit of our solution. 
Result so far: 3.0
Deduct 36 from 39 and we're left with 3.
Include the next digit (9) from the dividend after 3, then repeat: 39 / 12

On to step 3:
If we divide 39 by 12, we get 3 and a remainder of 3.
Put 3 as the next digit of the answer. 
Result so far: 33.0
The remainder is 3 after subtracting 36 from 39.
Append the next digit (1) from the dividend to 3 and continue with: 31 / 12

Advancing to step 4:
If we divide 31 by 12, we get 2 and a remainder of 7.
Use 2 as the next digit of our solution. 
Result so far: 332.0
Subtracting 24 from 31 leaves us with 7.
Fetch the next digit (9) from the dividend, attach it to 7 and continue: 79 / 12

Moving on to step 5:
12 can be fit into 79 6 times, resulting in a remainder of 7.
The number 6 becomes the next digit in our result. 
Result so far: 3326.0
Deduct 72 from 79 and we're left with 7.
Fetch the next digit (0) from the dividend, attach it to 7 and continue: 70 / 12

Moving on to step 6:
12 goes into 70 5 times with a remainder of 10.
Write down 5 as next digit of the result. 
Result so far: 33265.0
Deduct 60 from 70 and we're left with 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Step 7:
12 can be fit into 100 8 times, resulting in a remainder of 4.
Use 8 as the next digit of our solution. 
Result so far: 33265.8
If we subtract 96 from 100, we get 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Advancing to step 8:
12 goes into 40 3 times with a remainder of 4.
Put 3 as the next digit of the answer. 
Result so far: 33265.83
Deduct 36 from 40 and we're left with 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Step 9:
12 can be fit into 40 3 times, resulting in a remainder of 4.
Write down 3 as next digit of the result. 
Result so far: 33265.833
The remainder is 4 after subtracting 36 from 40.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

The final result is 33265.833 with a remainder of 0.0004.