129438 divided by 42 
The aim is to understand the frequency of 42 in 129438.

On to step 1:
When dividing 1 by 42, we get 0 with a remainder of 1.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Deduct 0 from 1 and we're left with 1.
Fetch the next digit (2) from the dividend, attach it to 1 and continue: 12 / 42

Going ahead to step 2:
When dividing 12 by 42, we get 0 with a remainder of 12.
The next digit of our result is 0. 
Result so far: 0.0
Deduct 0 from 12 and we're left with 12.
Fetch the next digit (9) from the dividend, attach it to 12 and continue: 129 / 42

On to step 3:
42 goes into 129 3 times with a remainder of 3.
Record the quotient 3 as the next digit in the result. 
Result so far: 3.0
The remainder is 3 after subtracting 126 from 129.
Bring next digit (4) of the dividend behind the 3 and repeat the process: 34 / 42

Going ahead to step 4:
42 goes into 34 0 times with a remainder of 34.
Write down 0 as next digit of the result. 
Result so far: 30.0
Subtract 0 from 34 to get 34.
Append the next digit (3) from the dividend to 34 and continue with: 343 / 42

On to step 5:
When dividing 343 by 42, we get 8 with a remainder of 7.
Put 8 as the next digit of the answer. 
Result so far: 308.0
Subtracting 336 from 343 leaves us with 7.
Bring next digit (8) of the dividend behind the 7 and repeat the process: 78 / 42

Let's proceed to step 6:
42 goes into 78 1 times with a remainder of 36.
Write down 1 as next digit of the result. 
Result so far: 3081.0
If we take 42 away from 78, we end up with 36.
Since there are no more digits in the dividend, we add a zero to the remainder making it 360, and continue the process.

Going ahead to step 7:
42 goes into 360 8 times with a remainder of 24.
Put 8 as the next digit of the answer. 
Result so far: 3081.8
If we take 336 away from 360, we end up with 24.
Since there are no more digits in the dividend, we add a zero to the remainder making it 240, and continue the process.

Moving on to step 8:
The number 42 fits into 240 5 times, leaving a remainder of 30.
The number 5 becomes the next digit in our result. 
Result so far: 3081.85
Subtract 210 from 240 to get 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 300, and continue the process.

Advancing to step 9:
300 divided by 42 is 7 with a remainder of 6.
Use 7 as the next digit of our solution. 
Result so far: 3081.857
The remainder is 6 after subtracting 294 from 300.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Step 10:
The number 42 fits into 60 1 times, leaving a remainder of 18.
Use 1 as the next digit of our solution. 
Result so far: 3081.8571
Deduct 42 from 60 and we're left with 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 11:
42 can be fit into 180 4 times, resulting in a remainder of 12.
The number 4 becomes the next digit in our result. 
Result so far: 3081.85714
Deduct 168 from 180 and we're left 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.

Moving on to step 12:
When dividing 120 by 42, we get 2 with a remainder of 36.
Write down 2 as next digit of the result. 
Result so far: 3081.857142
Subtract 84 from 120 to get 36.
Since there are no more digits in the dividend, we add a zero to the remainder making it 360, and continue the process.

On to step 13:
42 can be fit into 360 8 times, resulting in a remainder of 24.
Record the quotient 8 as the next digit in the result. 
Result so far: 3081.8571428
Subtracting 336 from 360 leaves us with 24.
Since there are no more digits in the dividend, we add a zero to the remainder making it 240, and continue the process.

On to step 14:
240 divided by 42 is 5 with a remainder of 30.
Use 5 as the next digit of our solution. 
Result so far: 3081.85714285
If we take 210 away from 240, we end up with 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 300, and continue the process.

The final result is 3081.85714285 with a remainder of 3e-08.