We're dividing 648573 by 51 
We want to figure out the number of times 648573 can be divided by 51.

Step 1:
When dividing 6 by 51, we get 0 with a remainder of 6.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
If we take 0 away from 6, we end up with 6.
Take the next digit (4) from the dividend and append it to 6, then repeat: 64 / 51

On to step 2:
When dividing 64 by 51, we get 1 with a remainder of 13.
The next digit of our result is 1. 
Result so far: 1.0
Deduct 51 from 64 and we're left with 13.
Grab the next digit (8) from the dividend, add it to 13, then carry on: 138 / 51

Going ahead to step 3:
When dividing 138 by 51, we get 2 with a remainder of 36.
Record the quotient 2 as the next digit in the result. 
Result so far: 12.0
Subtracting 102 from 138 leaves us with 36.
Fetch the next digit (5) from the dividend, attach it to 36 and continue: 365 / 51

Moving on to step 4:
51 can be fit into 365 7 times, resulting in a remainder of 8.
Put 7 as the next digit of the answer. 
Result so far: 127.0
Subtract 357 from 365 to get 8.
Grab the next digit (7) from the dividend, add it to 8, then carry on: 87 / 51

Moving on to step 5:
51 goes into 87 1 times with a remainder of 36.
Record the quotient 1 as the next digit in the result. 
Result so far: 1271.0
If we take 51 away from 87, we end up with 36.
Include the next digit (3) from the dividend after 36, then repeat: 363 / 51

Advancing to step 6:
The number 51 fits into 363 7 times, leaving a remainder of 6.
The number 7 becomes the next digit in our result. 
Result so far: 12717.0
If we take 357 away from 363, we end up with 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Advancing to step 7:
60 divided by 51 is 1 with a remainder of 9.
Use 1 as the next digit of our solution. 
Result so far: 12717.1
Subtract 51 from 60 to get 9.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

On to step 8:
The number 51 fits into 90 1 times, leaving a remainder of 39.
The number 1 becomes the next digit in our result. 
Result so far: 12717.11
Subtracting 51 from 90 leaves us 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.

The final result is 12717.11 with a remainder of 0.039.