We're dividing 663991 by 80 
We're looking to find how many times 80 goes into 663991.

Going ahead to step 1:
If we divide 6 by 80, we get 0 and a remainder of 6.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Subtracting 0 from 6 leaves us with 6.
Append the next digit (6) from the dividend to 6 and continue with: 66 / 80

Moving on to step 2:
80 goes into 66 0 times with a remainder of 66.
Write down 0 as next digit of the result. 
Result so far: 0.0
The remainder is 66 after subtracting 0 from 66.
Append the next digit (3) from the dividend to 66 and continue with: 663 / 80

Advancing to step 3:
80 goes into 663 8 times with a remainder of 23.
The next digit of our result is 8. 
Result so far: 8.0
Subtracting 640 from 663 leaves us with 23.
Bring next digit (9) of the dividend behind the 23 and repeat the process: 239 / 80

Let's proceed to step 4:
The number 80 fits into 239 2 times, leaving a remainder of 79.
Write down 2 as next digit of the result. 
Result so far: 82.0
Deduct 160 from 239 and we're left with 79.
Take the next digit (9) from the dividend and append it to 79, then repeat: 799 / 80

Step 5:
The number 80 fits into 799 9 times, leaving a remainder of 79.
The next digit of our result is 9. 
Result so far: 829.0
If we take 720 away from 799, we end up with 79.
Bring next digit (1) of the dividend behind the 79 and repeat the process: 791 / 80

Advancing to step 6:
The number 80 fits into 791 9 times, leaving a remainder of 71.
The number 9 becomes the next digit in our result. 
Result so far: 8299.0
Subtract 720 from 791 to get 71.
Since there are no more digits in the dividend, we add a zero to the remainder making it 710, and continue the process.

On to step 7:
80 can be fit into 710 8 times, resulting in a remainder of 70.
The number 8 becomes the next digit in our result. 
Result so far: 8299.8
Deduct 640 from 710 and we're left with 70.
Since there are no more digits in the dividend, we add a zero to the remainder making it 700, and continue the process.

Advancing to step 8:
700 divided by 80 is 8 with a remainder of 60.
The number 8 becomes the next digit in our result. 
Result so far: 8299.88
The remainder is 60 after subtracting 640 from 700.
Since there are no more digits in the dividend, we add a zero to the remainder making it 600, and continue the process.

Our division results in 8299.88 with a remaining 0.06.