We look at the division of 51870091 by 855 
The aim is to understand the frequency of 855 in 51870091.

On to step 1:
855 goes into 5 0 times 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 / 855

Let's proceed to step 2:
855 can be fit into 51 0 times, resulting in a remainder of 51.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Subtracting 0 from 51 leaves us with 51.
Bring next digit (8) of the dividend behind the 51 and repeat the process: 518 / 855

Moving on to step 3:
If we divide 518 by 855, we get 0 and a remainder of 518.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Deduct 0 from 518 and we're left with 518.
Take the next digit (7) from the dividend and append it to 518, then repeat: 5187 / 855

Advancing to step 4:
If we divide 5187 by 855, we get 6 and a remainder of 57.
Record the quotient 6 as the next digit in the result. 
Result so far: 6.0
Subtracting 5130 from 5187 leaves us with 57.
Take the next digit (0) from the dividend and append it to 57, then repeat: 570 / 855

Advancing to step 5:
When dividing 570 by 855, we get 0 with a remainder of 570.
Use 0 as the next digit of our solution. 
Result so far: 60.0
Subtracting 0 from 570 leaves us with 570.
Fetch the next digit (0) from the dividend, attach it to 570 and continue: 5700 / 855

Step 6:
855 can be fit into 5700 6 times, resulting in a remainder of 570.
The number 6 becomes the next digit in our result. 
Result so far: 606.0
Subtract 5130 from 5700 to get 570.
Bring next digit (9) of the dividend behind the 570 and repeat the process: 5709 / 855

Moving on to step 7:
855 goes into 5709 6 times with a remainder of 579.
Put 6 as the next digit of the answer. 
Result so far: 6066.0
Deduct 5130 from 5709 and we're left with 579.
Bring next digit (1) of the dividend behind the 579 and repeat the process: 5791 / 855

Moving on to step 8:
855 can be fit into 5791 6 times, resulting in a remainder of 661.
The next digit of our result is 6. 
Result so far: 60666.0
Deduct 5130 from 5791 and we're left with 661.
Since there are no more digits in the dividend, we add a zero to the remainder making it 6610, and continue the process.

Advancing to step 9:
If we divide 6610 by 855, we get 7 and a remainder of 625.
Write down 7 as next digit of the result. 
Result so far: 60666.7
The remainder is 625 after subtracting 5985 from 6610.
Since there are no more digits in the dividend, we add a zero to the remainder making it 6250, and continue the process.

Let's proceed to step 10:
855 goes into 6250 7 times with a remainder of 265.
Write down 7 as next digit of the result. 
Result so far: 60666.77
If we take 5985 away from 6250, we end up with 265.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2650, and continue the process.

After the division, we end up with 60666.77 and a remainder of 0.265.