We're dividing 251842 by 20 
The aim is to understand the frequency of 20 in 251842.

On to step 1:
20 goes into 2 0 times with a remainder of 2.
Put 0 as the next digit of the answer. 
Result so far: 0.0
If we take 0 away from 2, we end up with 2.
Include the next digit (5) from the dividend after 2, then repeat: 25 / 20

Moving on to step 2:
If we divide 25 by 20, we get 1 and a remainder of 5.
Record the quotient 1 as the next digit in the result. 
Result so far: 1.0
Subtract 20 from 25 to get 5.
Append the next digit (1) from the dividend to 5 and continue with: 51 / 20

Advancing to step 3:
When dividing 51 by 20, we get 2 with a remainder of 11.
Record the quotient 2 as the next digit in the result. 
Result so far: 12.0
Subtract 40 from 51 to get 11.
Grab the next digit (8) from the dividend, add it to 11, then carry on: 118 / 20

Step 4:
20 goes into 118 5 times with a remainder of 18.
Put 5 as the next digit of the answer. 
Result so far: 125.0
Deduct 100 from 118 and we're left with 18.
Grab the next digit (4) from the dividend, add it to 18, then carry on: 184 / 20

Moving on to step 5:
184 divided by 20 is 9 with a remainder of 4.
The number 9 becomes the next digit in our result. 
Result so far: 1259.0
If we subtract 180 from 184, we get 4.
Grab the next digit (2) from the dividend, add it to 4, then carry on: 42 / 20

Going ahead to step 6:
When dividing 42 by 20, we get 2 with a remainder of 2.
The number 2 becomes the next digit in our result. 
Result so far: 12592.0
If we take 40 away from 42, we end up with 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

On to step 7:
20 can be fit into 20 1 times, resulting in a remainder of 0.
The number 1 becomes the next digit in our result. 
Result so far: 12592.1
If we subtract 20 from 20, we get 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Advancing to step 8:
When dividing 0 by 20, we get 0 with a remainder of 0.
Record the quotient 0 as the next digit in the result. 
Result so far: 12592.1
If we take 0 away from 0, we end up with 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Going ahead to step 9:
The number 20 fits into 0 0 times, leaving a remainder of 0.
Write down 0 as next digit of the result. 
Result so far: 12592.1
If we take 0 away from 0, we end up with 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

The final outcome is 12592.1, with a leftover of 0.0.