We're dividing 91851709 by 121 
We want to figure out the number of times 91851709 can be divided by 121.

Step 1:
When dividing 9 by 121, we get 0 with a remainder of 9.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Deduct 0 from 9 and we're left with 9.
Include the next digit (1) from the dividend after 9, then repeat: 91 / 121

Moving on to step 2:
121 can be fit into 91 0 times, resulting in a remainder of 91.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
The remainder is 91 after subtracting 0 from 91.
Fetch the next digit (8) from the dividend, attach it to 91 and continue: 918 / 121

Advancing to step 3:
If we divide 918 by 121, we get 7 and a remainder of 71.
The number 7 becomes the next digit in our result. 
Result so far: 7.0
The remainder is 71 after subtracting 847 from 918.
Take the next digit (5) from the dividend and append it to 71, then repeat: 715 / 121

On to step 4:
121 can be fit into 715 5 times, resulting in a remainder of 110.
The next digit of our result is 5. 
Result so far: 75.0
If we take 605 away from 715, we end up with 110.
Fetch the next digit (1) from the dividend, attach it to 110 and continue: 1101 / 121

On to step 5:
1101 divided by 121 is 9 with a remainder of 12.
Write down 9 as next digit of the result. 
Result so far: 759.0
Deduct 1089 from 1101 and we're left with 12.
Grab the next digit (7) from the dividend, add it to 12, then carry on: 127 / 121

Advancing to step 6:
If we divide 127 by 121, we get 1 and a remainder of 6.
Record the quotient 1 as the next digit in the result. 
Result so far: 7591.0
Subtracting 121 from 127 leaves us with 6.
Append the next digit (0) from the dividend to 6 and continue with: 60 / 121

Step 7:
If we divide 60 by 121, we get 0 and a remainder of 60.
The number 0 becomes the next digit in our result. 
Result so far: 75910.0
If we subtract 0 from 60, we get 60.
Include the next digit (9) from the dividend after 60, then repeat: 609 / 121

Moving on to step 8:
609 divided by 121 is 5 with a remainder of 4.
Use 5 as the next digit of our solution. 
Result so far: 759105.0
Subtract 605 from 609 to get 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

On to step 9:
40 divided by 121 is 0 with a remainder of 40.
Use 0 as the next digit of our solution. 
Result so far: 759105.0
Subtract 0 from 40 to get 40.
Since there are no more digits in the dividend, we add a zero to the remainder making it 400, and continue the process.

Advancing to step 10:
If we divide 400 by 121, we get 3 and a remainder of 37.
Put 3 as the next digit of the answer. 
Result so far: 759105.03
Subtracting 363 from 400 leaves us with 37.
Since there are no more digits in the dividend, we add a zero to the remainder making it 370, and continue the process.

Step 11:
If we divide 370 by 121, we get 3 and a remainder of 7.
The number 3 becomes the next digit in our result. 
Result so far: 759105.033
Subtract 363 from 370 to get 7.
Since there are no more digits in the dividend, we add a zero to the remainder making it 70, and continue the process.

The final outcome is 759105.033, with a leftover of 0.0007.