We look at the division of 91578009 by 71 
The aim is to understand the frequency of 71 in 91578009.

On to step 1:
71 can be fit into 9 0 times, resulting in a remainder of 9.
Write down 0 as next digit of the result. 
Result so far: 0.0
If we take 0 away from 9, we end up with 9.
Grab the next digit (1) from the dividend, add it to 9, then carry on: 91 / 71

Moving on to step 2:
If we divide 91 by 71, we get 1 and a remainder of 20.
The next digit of our result is 1. 
Result so far: 1.0
The remainder is 20 after subtracting 71 from 91.
Fetch the next digit (5) from the dividend, attach it to 20 and continue: 205 / 71

Let's proceed to step 3:
If we divide 205 by 71, we get 2 and a remainder of 63.
The next digit of our result is 2. 
Result so far: 12.0
If we take 142 away from 205, we end up with 63.
Bring next digit (7) of the dividend behind the 63 and repeat the process: 637 / 71

Let's proceed to step 4:
637 divided by 71 is 8 with a remainder of 69.
Record the quotient 8 as the next digit in the result. 
Result so far: 128.0
Subtracting 568 from 637 leaves us with 69.
Append the next digit (8) from the dividend to 69 and continue with: 698 / 71

Moving on to step 5:
71 can be fit into 698 9 times, resulting in a remainder of 59.
Record the quotient 9 as the next digit in the result. 
Result so far: 1289.0
The remainder is 59 after subtracting 639 from 698.
Append the next digit (0) from the dividend to 59 and continue with: 590 / 71

Let's proceed to step 6:
71 can be fit into 590 8 times, resulting in a remainder of 22.
Record the quotient 8 as the next digit in the result. 
Result so far: 12898.0
Subtract 568 from 590 to get 22.
Include the next digit (0) from the dividend after 22, then repeat: 220 / 71

Moving on to step 7:
220 divided by 71 is 3 with a remainder of 7.
The number 3 becomes the next digit in our result. 
Result so far: 128983.0
Deduct 213 from 220 and we're left with 7.
Include the next digit (9) from the dividend after 7, then repeat: 79 / 71

Let's proceed to step 8:
79 divided by 71 is 1 with a remainder of 8.
Use 1 as the next digit of our solution. 
Result so far: 1289831.0
Subtracting 71 from 79 leaves us with 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Moving on to step 9:
71 goes into 80 1 times with a remainder of 9.
Record the quotient 1 as the next digit in the result. 
Result so far: 1289831.1
Deduct 71 from 80 and we're left with 9.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

Moving on to step 10:
The number 71 fits into 90 1 times, leaving a remainder of 19.
The number 1 becomes the next digit in our result. 
Result so far: 1289831.11
Subtract 71 from 90 to get 19.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

The quotient of the division is 1289831.11, and the remainder is 0.019.