We look at the division of 434448 by 21 
The aim is to understand the frequency of 21 in 434448.

On to step 1:
When dividing 4 by 21, we get 0 with a remainder of 4.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Subtract 0 from 4 to get 4.
Fetch the next digit (3) from the dividend, attach it to 4 and continue: 43 / 21

Going ahead to step 2:
21 goes into 43 2 times with a remainder of 1.
Record the quotient 2 as the next digit in the result. 
Result so far: 2.0
If we subtract 42 from 43, we get 1.
Append the next digit (4) from the dividend to 1 and continue with: 14 / 21

Let's proceed to step 3:
If we divide 14 by 21, we get 0 and a remainder of 14.
Record the quotient 0 as the next digit in the result. 
Result so far: 20.0
Subtract 0 from 14 to get 14.
Append the next digit (4) from the dividend to 14 and continue with: 144 / 21

Moving on to step 4:
When dividing 144 by 21, we get 6 with a remainder of 18.
Record the quotient 6 as the next digit in the result. 
Result so far: 206.0
If we take 126 away from 144, we end up with 18.
Fetch the next digit (4) from the dividend, attach it to 18 and continue: 184 / 21

Going ahead to step 5:
When dividing 184 by 21, we get 8 with a remainder of 16.
Use 8 as the next digit of our solution. 
Result so far: 2068.0
Subtract 168 from 184 to get 16.
Take the next digit (8) from the dividend and append it to 16, then repeat: 168 / 21

On to step 6:
If we divide 168 by 21, we get 8 and a remainder of 0.
The number 8 becomes the next digit in our result. 
Result so far: 20688.0
Subtract 168 from 168 to 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 7:
The number 21 fits into 0 0 times, leaving a remainder of 0.
Put 0 as the next digit of the answer. 
Result so far: 20688.0
Subtract 0 from 0 to 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.

Step 8:
21 goes into 0 0 times with a remainder of 0.
Write down 0 as next digit of the result. 
Result so far: 20688.0
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.

In conclusion, the division gives 20688.0 with a balance of 0.0.