Let's divide 157485 by 21
The aim is to understand the frequency of 21 in 157485.

Moving on to step 1:
If we divide 1 by 21, we get 0 and a remainder of 1.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
The remainder is 1 after subtracting 0 from 1.
Grab the next digit (5) from the dividend, add it to 1, then carry on: 15 / 21

On to step 2:
The number 21 fits into 15 0 times, leaving a remainder of 15.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Subtracting 0 from 15 leaves us with 15.
Bring next digit (7) of the dividend behind the 15 and repeat the process: 157 / 21

Moving on to step 3:
157 divided by 21 is 7 with a remainder of 10.
Record the quotient 7 as the next digit in the result. 
Result so far: 7.0
Deduct 147 from 157 and we're left with 10.
Take the next digit (4) from the dividend and append it to 10, then repeat: 104 / 21

Moving on to step 4:
21 goes into 104 4 times with a remainder of 20.
Record the quotient 4 as the next digit in the result. 
Result so far: 74.0
Deduct 84 from 104 and we're left with 20.
Grab the next digit (8) from the dividend, add it to 20, then carry on: 208 / 21

Advancing to step 5:
If we divide 208 by 21, we get 9 and a remainder of 19.
The next digit of our result is 9. 
Result so far: 749.0
The remainder is 19 after subtracting 189 from 208.
Take the next digit (5) from the dividend and append it to 19, then repeat: 195 / 21

Moving on to step 6:
21 goes into 195 9 times with a remainder of 6.
Use 9 as the next digit of our solution. 
Result so far: 7499.0
If we subtract 189 from 195, we get 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Moving on to step 7:
21 goes into 60 2 times with a remainder of 18.
The next digit of our result is 2. 
Result so far: 7499.2
Subtract 42 from 60 to get 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

On to step 8:
The number 21 fits into 180 8 times, leaving a remainder of 12.
The number 8 becomes the next digit in our result. 
Result so far: 7499.28
Subtracting 168 from 180 leaves us with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Going ahead to step 9:
If we divide 120 by 21, we get 5 and a remainder of 15.
Use 5 as the next digit of our solution. 
Result so far: 7499.285
If we take 105 away from 120, we end up with 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Going ahead to step 10:
When dividing 150 by 21, we get 7 with a remainder of 3.
Use 7 as the next digit of our solution. 
Result so far: 7499.2857
The remainder is 3 after subtracting 147 from 150.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Moving on to step 11:
21 goes into 30 1 times with a remainder of 9.
The next digit of our result is 1. 
Result so far: 7499.28571
Deduct 21 from 30 and we're left with 9.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

Step 12:
The number 21 fits into 90 4 times, leaving a remainder of 6.
The next digit of our result is 4. 
Result so far: 7499.285714
If we take 84 away from 90, we end up with 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

On to step 13:
21 can be fit into 60 2 times, resulting in a remainder of 18.
Put 2 as the next digit of the answer. 
Result so far: 7499.2857142
If we subtract 42 from 60, we get 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

Going ahead to step 14:
21 goes into 180 8 times with a remainder of 12.
Put 8 as the next digit of the answer. 
Result so far: 7499.28571428
Subtracting 168 from 180 leaves us with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

The final result is 7499.28571428 with a remainder of 1.2e-08.