We look at the division of 12688087 by 603 
The aim is to understand the frequency of 603 in 12688087.

On to step 1:
603 goes into 1 0 times with 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.
Include the next digit (2) from the dividend after 1, then repeat: 12 / 603

Going ahead to step 2:
603 goes into 12 0 times with a remainder of 12.
Put 0 as the next digit of the answer. 
Result so far: 0.0
The remainder is 12 after subtracting 0 from 12.
Fetch the next digit (6) from the dividend, attach it to 12 and continue: 126 / 603

Moving on to step 3:
If we divide 126 by 603, we get 0 and a remainder of 126.
The next digit of our result is 0. 
Result so far: 0.0
Subtracting 0 from 126 leaves us with 126.
Take the next digit (8) from the dividend and append it to 126, then repeat: 1268 / 603

On to step 4:
The number 603 fits into 1268 2 times, leaving a remainder of 62.
Write down 2 as next digit of the result. 
Result so far: 2.0
Deduct 1206 from 1268 and we're left with 62.
Take the next digit (8) from the dividend and append it to 62, then repeat: 628 / 603

On to step 5:
When dividing 628 by 603, we get 1 with a remainder of 25.
The number 1 becomes the next digit in our result. 
Result so far: 21.0
If we subtract 603 from 628, we get 25.
Fetch the next digit (0) from the dividend, attach it to 25 and continue: 250 / 603

Step 6:
If we divide 250 by 603, we get 0 and a remainder of 250.
Put 0 as the next digit of the answer. 
Result so far: 210.0
Subtract 0 from 250 to get 250.
Append the next digit (8) from the dividend to 250 and continue with: 2508 / 603

On to step 7:
603 can be fit into 2508 4 times, resulting in a remainder of 96.
Put 4 as the next digit of the answer. 
Result so far: 2104.0
If we subtract 2412 from 2508, we get 96.
Grab the next digit (7) from the dividend, add it to 96, then carry on: 967 / 603

Advancing to step 8:
967 divided by 603 is 1 with a remainder of 364.
Put 1 as the next digit of the answer. 
Result so far: 21041.0
The remainder is 364 after subtracting 603 from 967.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3640, and continue the process.

On to step 9:
If we divide 3640 by 603, we get 6 and a remainder of 22.
Put 6 as the next digit of the answer. 
Result so far: 21041.6
If we take 3618 away from 3640, we end up with 22.
Since there are no more digits in the dividend, we add a zero to the remainder making it 220, and continue the process.

Step 10:
If we divide 220 by 603, we get 0 and a remainder of 220.
Use 0 as the next digit of our solution. 
Result so far: 21041.6
Subtracting 0 from 220 leaves us with 220.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2200, and continue the process.

Going ahead to step 11:
603 can be fit into 2200 3 times, resulting in a remainder of 391.
Write down 3 as next digit of the result. 
Result so far: 21041.603
Subtract 1809 from 2200 to get 391.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3910, and continue the process.

Advancing to step 12:
The number 603 fits into 3910 6 times, leaving a remainder of 292.
The number 6 becomes the next digit in our result. 
Result so far: 21041.6036
If we take 3618 away from 3910, we end up with 292.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2920, and continue the process.

Step 13:
2920 divided by 603 is 4 with a remainder of 508.
Write down 4 as next digit of the result. 
Result so far: 21041.60364
Deduct 2412 from 2920 and we're left with 508.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5080, and continue the process.

On to step 14:
5080 divided by 603 is 8 with a remainder of 256.
Put 8 as the next digit of the answer. 
Result so far: 21041.603648
If we subtract 4824 from 5080, we get 256.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2560, and continue the process.

Moving on to step 15:
603 goes into 2560 4 times with a remainder of 148.
Use 4 as the next digit of our solution. 
Result so far: 21041.6036484
Subtracting 2412 from 2560 leaves us with 148.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1480, and continue the process.

Going ahead to step 16:
When dividing 1480 by 603, we get 2 with a remainder of 274.
Record the quotient 2 as the next digit in the result. 
Result so far: 21041.60364842
If we take 1206 away from 1480, we end up with 274.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2740, and continue the process.

The final result is 21041.60364842 with a remainder of 2.74e-07.