51118479 ÷ 399 
We want to divide 51118479 by 399.

Moving on to step 1:
When dividing 5 by 399, we get 0 with a remainder of 5.
The next digit of our result is 0. 
Result so far: 0.0
If we subtract 0 from 5, we get 5.
Grab the next digit (1) from the dividend, add it to 5, then carry on: 51 / 399

On to step 2:
399 goes into 51 0 times with a remainder of 51.
The next digit of our result is 0. 
Result so far: 0.0
If we subtract 0 from 51, we get 51.
Grab the next digit (1) from the dividend, add it to 51, then carry on: 511 / 399

Advancing to step 3:
When dividing 511 by 399, we get 1 with a remainder of 112.
The next digit of our result is 1. 
Result so far: 1.0
Deduct 399 from 511 and we're left with 112.
Fetch the next digit (1) from the dividend, attach it to 112 and continue: 1121 / 399

Let's proceed to step 4:
399 goes into 1121 2 times with a remainder of 323.
The next digit of our result is 2. 
Result so far: 12.0
Subtract 798 from 1121 to get 323.
Include the next digit (8) from the dividend after 323, then repeat: 3238 / 399

Advancing to step 5:
3238 divided by 399 is 8 with a remainder of 46.
Write down 8 as next digit of the result. 
Result so far: 128.0
Subtracting 3192 from 3238 leaves us with 46.
Grab the next digit (4) from the dividend, add it to 46, then carry on: 464 / 399

Advancing to step 6:
464 divided by 399 is 1 with a remainder of 65.
Put 1 as the next digit of the answer. 
Result so far: 1281.0
Subtracting 399 from 464 leaves us with 65.
Append the next digit (7) from the dividend to 65 and continue with: 657 / 399

Let's proceed to step 7:
399 can be fit into 657 1 times, resulting in a remainder of 258.
Use 1 as the next digit of our solution. 
Result so far: 12811.0
Subtract 399 from 657 to get 258.
Bring next digit (9) of the dividend behind the 258 and repeat the process: 2589 / 399

Step 8:
2589 divided by 399 is 6 with a remainder of 195.
Put 6 as the next digit of the answer. 
Result so far: 128116.0
Deduct 2394 from 2589 and we're left with 195.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1950, and continue the process.

On to step 9:
399 can be fit into 1950 4 times, resulting in a remainder of 354.
Use 4 as the next digit of our solution. 
Result so far: 128116.4
If we subtract 1596 from 1950, we get 354.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3540, and continue the process.

Going ahead to step 10:
399 goes into 3540 8 times with a remainder of 348.
Use 8 as the next digit of our solution. 
Result so far: 128116.48
The remainder is 348 after subtracting 3192 from 3540.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3480, and continue the process.

Moving on to step 11:
If we divide 3480 by 399, we get 8 and a remainder of 288.
Write down 8 as next digit of the result. 
Result so far: 128116.488
The remainder is 288 after subtracting 3192 from 3480.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2880, and continue the process.

The final result is 128116.488 with a remainder of 0.0288.