312291 divided by 87 
The aim is to understand the frequency of 87 in 312291.

On to step 1:
87 goes into 3 0 times with a remainder of 3.
Write down 0 as next digit of the result. 
Result so far: 0.0
Deduct 0 from 3 and we're left with 3.
Grab the next digit (1) from the dividend, add it to 3, then carry on: 31 / 87

Advancing to step 2:
When dividing 31 by 87, we get 0 with a remainder of 31.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtract 0 from 31 to get 31.
Append the next digit (2) from the dividend to 31 and continue with: 312 / 87

On to step 3:
The number 87 fits into 312 3 times, leaving a remainder of 51.
Use 3 as the next digit of our solution. 
Result so far: 3.0
If we take 261 away from 312, we end up with 51.
Bring next digit (2) of the dividend behind the 51 and repeat the process: 512 / 87

Moving on to step 4:
If we divide 512 by 87, we get 5 and a remainder of 77.
Write down 5 as next digit of the result. 
Result so far: 35.0
Subtracting 435 from 512 leaves us with 77.
Grab the next digit (9) from the dividend, add it to 77, then carry on: 779 / 87

Step 5:
87 can be fit into 779 8 times, resulting in a remainder of 83.
The number 8 becomes the next digit in our result. 
Result so far: 358.0
Subtracting 696 from 779 leaves us with 83.
Bring next digit (1) of the dividend behind the 83 and repeat the process: 831 / 87

Step 6:
87 goes into 831 9 times with a remainder of 48.
Record the quotient 9 as the next digit in the result. 
Result so far: 3589.0
If we take 783 away from 831, we end up with 48.
Since there are no more digits in the dividend, we add a zero to the remainder making it 480, and continue the process.

Going ahead to step 7:
87 can be fit into 480 5 times, resulting in a remainder of 45.
Put 5 as the next digit of the answer. 
Result so far: 3589.5
If we take 435 away from 480, we end up with 45.
Since there are no more digits in the dividend, we add a zero to the remainder making it 450, and continue the process.

Moving on to step 8:
The number 87 fits into 450 5 times, leaving a remainder of 15.
Put 5 as the next digit of the answer. 
Result so far: 3589.55
Subtract 435 from 450 to get 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

After the division, we end up with 3589.55 and a remainder of 0.015.