We look at the division of 509951 by 86 
Let's see how many times 86 fits into 509951.

Advancing to step 1:
86 goes into 5 0 times with a remainder of 5.
Put 0 as the next digit of the answer. 
Result so far: 0.0
If we subtract 0 from 5, we get 5.
Bring next digit (0) of the dividend behind the 5 and repeat the process: 50 / 86

Step 2:
50 divided by 86 is 0 with a remainder of 50.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
The remainder is 50 after subtracting 0 from 50.
Include the next digit (9) from the dividend after 50, then repeat: 509 / 86

Going ahead to step 3:
86 can be fit into 509 5 times, resulting in a remainder of 79.
Use 5 as the next digit of our solution. 
Result so far: 5.0
Subtracting 430 from 509 leaves us with 79.
Append the next digit (9) from the dividend to 79 and continue with: 799 / 86

On to step 4:
When dividing 799 by 86, we get 9 with a remainder of 25.
Write down 9 as next digit of the result. 
Result so far: 59.0
If we take 774 away from 799, we end up with 25.
Bring next digit (5) of the dividend behind the 25 and repeat the process: 255 / 86

On to step 5:
When dividing 255 by 86, we get 2 with a remainder of 83.
Use 2 as the next digit of our solution. 
Result so far: 592.0
If we subtract 172 from 255, we get 83.
Include the next digit (1) from the dividend after 83, then repeat: 831 / 86

Going ahead to step 6:
When dividing 831 by 86, we get 9 with a remainder of 57.
The next digit of our result is 9. 
Result so far: 5929.0
Subtracting 774 from 831 leaves us with 57.
Since there are no more digits in the dividend, we add a zero to the remainder making it 570, and continue the process.

Advancing to step 7:
The number 86 fits into 570 6 times, leaving a remainder of 54.
The number 6 becomes the next digit in our result. 
Result so far: 5929.6
If we take 516 away from 570, we end up with 54.
Since there are no more digits in the dividend, we add a zero to the remainder making it 540, and continue the process.

Let's proceed to step 8:
The number 86 fits into 540 6 times, leaving a remainder of 24.
Record the quotient 6 as the next digit in the result. 
Result so far: 5929.66
If we take 516 away from 540, we end up with 24.
Since there are no more digits in the dividend, we add a zero to the remainder making it 240, and continue the process.

After the division, we end up with 5929.66 and a remainder of 0.024.