We look at the division of 72428523 by 31 
The aim is to understand the frequency of 31 in 72428523.

Advancing to step 1:
When dividing 7 by 31, we get 0 with a remainder of 7.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
If we take 0 away from 7, we end up with 7.
Include the next digit (2) from the dividend after 7, then repeat: 72 / 31

Advancing to step 2:
72 divided by 31 is 2 with a remainder of 10.
Record the quotient 2 as the next digit in the result. 
Result so far: 2.0
Subtract 62 from 72 to get 10.
Append the next digit (4) from the dividend to 10 and continue with: 104 / 31

Moving on to step 3:
If we divide 104 by 31, we get 3 and a remainder of 11.
Record the quotient 3 as the next digit in the result. 
Result so far: 23.0
Subtract 93 from 104 to get 11.
Bring next digit (2) of the dividend behind the 11 and repeat the process: 112 / 31

Moving on to step 4:
The number 31 fits into 112 3 times, leaving a remainder of 19.
Record the quotient 3 as the next digit in the result. 
Result so far: 233.0
If we subtract 93 from 112, we get 19.
Bring next digit (8) of the dividend behind the 19 and repeat the process: 198 / 31

Step 5:
31 goes into 198 6 times with a remainder of 12.
The number 6 becomes the next digit in our result. 
Result so far: 2336.0
Subtracting 186 from 198 leaves us with 12.
Include the next digit (5) from the dividend after 12, then repeat: 125 / 31

Step 6:
31 goes into 125 4 times with a remainder of 1.
Use 4 as the next digit of our solution. 
Result so far: 23364.0
Subtracting 124 from 125 leaves us with 1.
Include the next digit (2) from the dividend after 1, then repeat: 12 / 31

Let's proceed to step 7:
12 divided by 31 is 0 with a remainder of 12.
Write down 0 as next digit of the result. 
Result so far: 233640.0
If we subtract 0 from 12, we get 12.
Include the next digit (3) from the dividend after 12, then repeat: 123 / 31

Step 8:
The number 31 fits into 123 3 times, leaving a remainder of 30.
Use 3 as the next digit of our solution. 
Result so far: 2336403.0
Subtract 93 from 123 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.

On to step 9:
The number 31 fits into 300 9 times, leaving a remainder of 21.
Write down 9 as next digit of the result. 
Result so far: 2336403.9
If we subtract 279 from 300, we get 21.
Since there are no more digits in the dividend, we add a zero to the remainder making it 210, and continue the process.

Moving on to step 10:
The number 31 fits into 210 6 times, leaving a remainder of 24.
Write down 6 as next digit of the result. 
Result so far: 2336403.96
If we subtract 186 from 210, we get 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 11:
If we divide 240 by 31, we get 7 and a remainder of 23.
Put 7 as the next digit of the answer. 
Result so far: 2336403.967
The remainder is 23 after subtracting 217 from 240.
Since there are no more digits in the dividend, we add a zero to the remainder making it 230, and continue the process.

On to step 12:
The number 31 fits into 230 7 times, leaving a remainder of 13.
The number 7 becomes the next digit in our result. 
Result so far: 2336403.9677
Subtracting 217 from 230 leaves us with 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

The quotient of the division is 2336403.9677, and the remainder is 0.00013.