12884987 ÷ 840 
Our goal is to divide 12884987 by 840.

Going ahead to step 1:
840 can be fit into 1 0 times, resulting in a remainder of 1.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Subtract 0 from 1 to get 1.
Take the next digit (2) from the dividend and append it to 1, then repeat: 12 / 840

On to step 2:
The number 840 fits into 12 0 times, leaving a remainder of 12.
Write down 0 as next digit of the result. 
Result so far: 0.0
Deduct 0 from 12 and we're left with 12.
Fetch the next digit (8) from the dividend, attach it to 12 and continue: 128 / 840

Advancing to step 3:
If we divide 128 by 840, we get 0 and a remainder of 128.
The next digit of our result is 0. 
Result so far: 0.0
If we take 0 away from 128, we end up with 128.
Fetch the next digit (8) from the dividend, attach it to 128 and continue: 1288 / 840

Advancing to step 4:
If we divide 1288 by 840, we get 1 and a remainder of 448.
Record the quotient 1 as the next digit in the result. 
Result so far: 1.0
If we subtract 840 from 1288, we get 448.
Bring next digit (4) of the dividend behind the 448 and repeat the process: 4484 / 840

Let's proceed to step 5:
If we divide 4484 by 840, we get 5 and a remainder of 284.
The number 5 becomes the next digit in our result. 
Result so far: 15.0
Deduct 4200 from 4484 and we're left with 284.
Grab the next digit (9) from the dividend, add it to 284, then carry on: 2849 / 840

Moving on to step 6:
The number 840 fits into 2849 3 times, leaving a remainder of 329.
Put 3 as the next digit of the answer. 
Result so far: 153.0
If we take 2520 away from 2849, we end up with 329.
Append the next digit (8) from the dividend to 329 and continue with: 3298 / 840

Step 7:
When dividing 3298 by 840, we get 3 with a remainder of 778.
Write down 3 as next digit of the result. 
Result so far: 1533.0
Deduct 2520 from 3298 and we're left with 778.
Append the next digit (7) from the dividend to 778 and continue with: 7787 / 840

Going ahead to step 8:
840 can be fit into 7787 9 times, resulting in a remainder of 227.
The next digit of our result is 9. 
Result so far: 15339.0
Deduct 7560 from 7787 and we're left with 227.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2270, and continue the process.

On to step 9:
840 can be fit into 2270 2 times, resulting in a remainder of 590.
Use 2 as the next digit of our solution. 
Result so far: 15339.2
If we subtract 1680 from 2270, we get 590.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5900, and continue the process.

Moving on to step 10:
5900 divided by 840 is 7 with a remainder of 20.
Use 7 as the next digit of our solution. 
Result so far: 15339.27
Subtract 5880 from 5900 to get 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Moving on to step 11:
When dividing 200 by 840, we get 0 with a remainder of 200.
Write down 0 as next digit of the result. 
Result so far: 15339.27
Subtracting 0 from 200 leaves us with 200.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2000, and continue the process.

On to step 12:
840 goes into 2000 2 times with a remainder of 320.
Record the quotient 2 as the next digit in the result. 
Result so far: 15339.2702
Subtracting 1680 from 2000 leaves us with 320.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3200, and continue the process.

Moving on to step 13:
840 goes into 3200 3 times with a remainder of 680.
The number 3 becomes the next digit in our result. 
Result so far: 15339.27023
Subtracting 2520 from 3200 leaves us with 680.
Since there are no more digits in the dividend, we add a zero to the remainder making it 6800, and continue the process.

Moving on to step 14:
If we divide 6800 by 840, we get 8 and a remainder of 80.
Write down 8 as next digit of the result. 
Result so far: 15339.270238
Subtract 6720 from 6800 to get 80.
Since there are no more digits in the dividend, we add a zero to the remainder making it 800, and continue the process.

On to step 15:
840 can be fit into 800 0 times, resulting in a remainder of 800.
The next digit of our result is 0. 
Result so far: 15339.270238
If we take 0 away from 800, we end up with 800.
Since there are no more digits in the dividend, we add a zero to the remainder making it 8000, and continue the process.

Let's proceed to step 16:
If we divide 8000 by 840, we get 9 and a remainder of 440.
Use 9 as the next digit of our solution. 
Result so far: 15339.27023809
Subtract 7560 from 8000 to get 440.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4400, and continue the process.

The final result is 15339.27023809 with a remainder of 4.4e-07.