We look at the division of 351580 by 42 
The aim is to understand the frequency of 42 in 351580.

Moving on to step 1:
3 divided by 42 is 0 with a remainder of 3.
Write down 0 as next digit of the result. 
Result so far: 0.0
Deduct 0 from 3 and we're left with 3.
Take the next digit (5) from the dividend and append it to 3, then repeat: 35 / 42

Moving on to step 2:
42 can be fit into 35 0 times, resulting in a remainder of 35.
The next digit of our result is 0. 
Result so far: 0.0
Subtracting 0 from 35 leaves us with 35.
Bring next digit (1) of the dividend behind the 35 and repeat the process: 351 / 42

On to step 3:
42 can be fit into 351 8 times, resulting in a remainder of 15.
Use 8 as the next digit of our solution. 
Result so far: 8.0
If we take 336 away from 351, we end up with 15.
Include the next digit (5) from the dividend after 15, then repeat: 155 / 42

Moving on to step 4:
42 can be fit into 155 3 times, resulting in a remainder of 29.
Put 3 as the next digit of the answer. 
Result so far: 83.0
If we take 126 away from 155, we end up with 29.
Bring next digit (8) of the dividend behind the 29 and repeat the process: 298 / 42

Let's proceed to step 5:
42 goes into 298 7 times with a remainder of 4.
Record the quotient 7 as the next digit in the result. 
Result so far: 837.0
Deduct 294 from 298 and we're left with 4.
Grab the next digit (0) from the dividend, add it to 4, then carry on: 40 / 42

Step 6:
42 can be fit into 40 0 times, resulting in a remainder of 40.
The number 0 becomes the next digit in our result. 
Result so far: 8370.0
Deduct 0 from 40 and we're left with 40.
Since there are no more digits in the dividend, we add a zero to the remainder making it 400, and continue the process.

Advancing to step 7:
42 goes into 400 9 times with a remainder of 22.
The next digit of our result is 9. 
Result so far: 8370.9
If we subtract 378 from 400, we get 22.
Since there are no more digits in the dividend, we add a zero to the remainder making it 220, and continue the process.

Going ahead to step 8:
220 divided by 42 is 5 with a remainder of 10.
Use 5 as the next digit of our solution. 
Result so far: 8370.95
If we subtract 210 from 220, we get 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Step 9:
100 divided by 42 is 2 with a remainder of 16.
Use 2 as the next digit of our solution. 
Result so far: 8370.952
Deduct 84 from 100 and we're left with 16.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

Let's proceed to step 10:
When dividing 160 by 42, we get 3 with a remainder of 34.
Put 3 as the next digit of the answer. 
Result so far: 8370.9523
Subtract 126 from 160 to get 34.
Since there are no more digits in the dividend, we add a zero to the remainder making it 340, and continue the process.

On to step 11:
The number 42 fits into 340 8 times, leaving a remainder of 4.
The next digit of our result is 8. 
Result so far: 8370.95238
If we take 336 away from 340, we end up with 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

On to step 12:
When dividing 40 by 42, we get 0 with a remainder of 40.
Record the quotient 0 as the next digit in the result. 
Result so far: 8370.95238
Subtracting 0 from 40 leaves us with 40.
Since there are no more digits in the dividend, we add a zero to the remainder making it 400, and continue the process.

Advancing to step 13:
42 can be fit into 400 9 times, resulting in a remainder of 22.
Record the quotient 9 as the next digit in the result. 
Result so far: 8370.9523809
If we take 378 away from 400, we end up with 22.
Since there are no more digits in the dividend, we add a zero to the remainder making it 220, and continue the process.

On to step 14:
If we divide 220 by 42, we get 5 and a remainder of 10.
Use 5 as the next digit of our solution. 
Result so far: 8370.95238095
Subtract 210 from 220 to get 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

The final outcome is 8370.95238095, with a leftover of 1e-08.