19991 ÷ 80 
We want to figure out the number of times 19991 can be divided by 80.

Step 1:
1 divided by 80 is 0 with a remainder of 1.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Deduct 0 from 1 and we're left with 1.
Include the next digit (9) from the dividend after 1, then repeat: 19 / 80

Step 2:
19 divided by 80 is 0 with a remainder of 19.
Use 0 as the next digit of our solution. 
Result so far: 0.0
The remainder is 19 after subtracting 0 from 19.
Bring next digit (9) of the dividend behind the 19 and repeat the process: 199 / 80

On to step 3:
80 can be fit into 199 2 times, resulting in a remainder of 39.
The number 2 becomes the next digit in our result. 
Result so far: 2.0
Subtract 160 from 199 to get 39.
Grab the next digit (9) from the dividend, add it to 39, then carry on: 399 / 80

On to step 4:
If we divide 399 by 80, we get 4 and a remainder of 79.
The number 4 becomes the next digit in our result. 
Result so far: 24.0
If we take 320 away from 399, we end up with 79.
Append the next digit (1) from the dividend to 79 and continue with: 791 / 80

On to step 5:
791 divided by 80 is 9 with a remainder of 71.
Record the quotient 9 as the next digit in the result. 
Result so far: 249.0
If we take 720 away from 791, we end up with 71.
Since there are no more digits in the dividend, we add a zero to the remainder making it 710, and continue the process.

Moving on to step 6:
710 divided by 80 is 8 with a remainder of 70.
Record the quotient 8 as the next digit in the result. 
Result so far: 249.8
The remainder is 70 after subtracting 640 from 710.
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 7:
700 divided by 80 is 8 with a remainder of 60.
Use 8 as the next digit of our solution. 
Result so far: 249.88
Subtract 640 from 700 to get 60.
Since there are no more digits in the dividend, we add a zero to the remainder making it 600, and continue the process.

The quotient of the division is 249.88, and the remainder is 0.06.