We divide 399403 by 31
We're looking to find how many times 31 goes into 399403.

On to step 1:
3 divided by 31 is 0 with a remainder of 3.
The next digit of our result is 0. 
Result so far: 0.0
Subtracting 0 from 3 leaves us with 3.
Take the next digit (9) from the dividend and append it to 3, then repeat: 39 / 31

Moving on to step 2:
When dividing 39 by 31, we get 1 with a remainder of 8.
The number 1 becomes the next digit in our result. 
Result so far: 1.0
If we take 31 away from 39, we end up with 8.
Take the next digit (9) from the dividend and append it to 8, then repeat: 89 / 31

Going ahead to step 3:
The number 31 fits into 89 2 times, leaving a remainder of 27.
Use 2 as the next digit of our solution. 
Result so far: 12.0
If we subtract 62 from 89, we get 27.
Take the next digit (4) from the dividend and append it to 27, then repeat: 274 / 31

Advancing to step 4:
31 goes into 274 8 times with a remainder of 26.
The next digit of our result is 8. 
Result so far: 128.0
Deduct 248 from 274 and we're left with 26.
Fetch the next digit (0) from the dividend, attach it to 26 and continue: 260 / 31

Let's proceed to step 5:
260 divided by 31 is 8 with a remainder of 12.
The number 8 becomes the next digit in our result. 
Result so far: 1288.0
Subtract 248 from 260 to get 12.
Include the next digit (3) from the dividend after 12, then repeat: 123 / 31

Step 6:
31 goes into 123 3 times with a remainder of 30.
Record the quotient 3 as the next digit in the result. 
Result so far: 12883.0
The remainder is 30 after subtracting 93 from 123.
Since there are no more digits in the dividend, we add a zero to the remainder making it 300, and continue the process.

Moving on to step 7:
31 goes into 300 9 times with a remainder of 21.
Record the quotient 9 as the next digit in the result. 
Result so far: 12883.9
If we subtract 279 from 300, we get 21.
Since there are no more digits in the dividend, we add a zero to the remainder making it 210, and continue the process.

Moving on to step 8:
210 divided by 31 is 6 with a remainder of 24.
Put 6 as the next digit of the answer. 
Result so far: 12883.96
Subtract 186 from 210 to get 24.
Since there are no more digits in the dividend, we add a zero to the remainder making it 240, and continue the process.

Step 9:
If we divide 240 by 31, we get 7 and a remainder of 23.
The number 7 becomes the next digit in our result. 
Result so far: 12883.967
Subtract 217 from 240 to get 23.
Since there are no more digits in the dividend, we add a zero to the remainder making it 230, and continue the process.

Advancing to step 10:
If we divide 230 by 31, we get 7 and a remainder of 13.
Use 7 as the next digit of our solution. 
Result so far: 12883.9677
If we take 217 away from 230, we end up with 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

The final result is 12883.9677 with a remainder of 0.00013.