We look at the division of 586521 by 78 
The aim is to understand the frequency of 78 in 586521.

Let's proceed to step 1:
If we divide 5 by 78, we get 0 and a remainder of 5.
The next digit of our result is 0. 
Result so far: 0.0
The remainder is 5 after subtracting 0 from 5.
Append the next digit (8) from the dividend to 5 and continue with: 58 / 78

Going ahead to step 2:
When dividing 58 by 78, we get 0 with a remainder of 58.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Subtracting 0 from 58 leaves us with 58.
Bring next digit (6) of the dividend behind the 58 and repeat the process: 586 / 78

Advancing to step 3:
If we divide 586 by 78, we get 7 and a remainder of 40.
Record the quotient 7 as the next digit in the result. 
Result so far: 7.0
The remainder is 40 after subtracting 546 from 586.
Include the next digit (5) from the dividend after 40, then repeat: 405 / 78

Let's proceed to step 4:
When dividing 405 by 78, we get 5 with a remainder of 15.
Write down 5 as next digit of the result. 
Result so far: 75.0
Subtract 390 from 405 to get 15.
Take the next digit (2) from the dividend and append it to 15, then repeat: 152 / 78

Going ahead to step 5:
The number 78 fits into 152 1 times, leaving a remainder of 74.
Put 1 as the next digit of the answer. 
Result so far: 751.0
If we take 78 away from 152, we end up with 74.
Append the next digit (1) from the dividend to 74 and continue with: 741 / 78

Step 6:
If we divide 741 by 78, we get 9 and a remainder of 39.
Use 9 as the next digit of our solution. 
Result so far: 7519.0
If we take 702 away from 741, we end up with 39.
Since there are no more digits in the dividend, we add a zero to the remainder making it 390, and continue the process.

Going ahead to step 7:
If we divide 390 by 78, we get 5 and a remainder of 0.
The next digit of our result is 5. 
Result so far: 7519.5
The remainder is 0 after subtracting 390 from 390.
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 8:
78 can be fit into 0 0 times, resulting in a remainder of 0.
The number 0 becomes the next digit in our result. 
Result so far: 7519.5
If we subtract 0 from 0, we 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.

Going ahead to step 9:
The number 78 fits into 0 0 times, leaving a remainder of 0.
Write down 0 as next digit of the result. 
Result so far: 7519.5
If we subtract 0 from 0, we 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.

The quotient of the division is 7519.5, and the remainder is 0.0.