We look at the division of 303237 by 15 
The aim is to understand the frequency of 15 in 303237.

On to step 1:
If we divide 3 by 15, we get 0 and a remainder of 3.
Use 0 as the next digit of our solution. 
Result so far: 0.0
If we take 0 away from 3, we end up with 3.
Fetch the next digit (0) from the dividend, attach it to 3 and continue: 30 / 15

On to step 2:
When dividing 30 by 15, we get 2 with a remainder of 0.
Record the quotient 2 as the next digit in the result. 
Result so far: 2.0
If we take 30 away from 30, we end up with 0.
Grab the next digit (3) from the dividend, add it to 0, then carry on: 3 / 15

Moving on to step 3:
3 divided by 15 is 0 with a remainder of 3.
Write down 0 as next digit of the result. 
Result so far: 20.0
The remainder is 3 after subtracting 0 from 3.
Fetch the next digit (2) from the dividend, attach it to 3 and continue: 32 / 15

Moving on to step 4:
If we divide 32 by 15, we get 2 and a remainder of 2.
Put 2 as the next digit of the answer. 
Result so far: 202.0
Subtracting 30 from 32 leaves us with 2.
Include the next digit (3) from the dividend after 2, then repeat: 23 / 15

Let's proceed to step 5:
15 goes into 23 1 times with a remainder of 8.
The next digit of our result is 1. 
Result so far: 2021.0
Subtracting 15 from 23 leaves us with 8.
Append the next digit (7) from the dividend to 8 and continue with: 87 / 15

Advancing to step 6:
15 can be fit into 87 5 times, resulting in a remainder of 12.
Put 5 as the next digit of the answer. 
Result so far: 20215.0
Subtracting 75 from 87 leaves us with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Let's proceed to step 7:
120 divided by 15 is 8 with a remainder of 0.
Use 8 as the next digit of our solution. 
Result so far: 20215.8
If we subtract 120 from 120, we get 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Moving on to step 8:
0 divided by 15 is 0 with a remainder of 0.
Write down 0 as next digit of the result. 
Result so far: 20215.8
If we take 0 away from 0, we end up with 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Moving on to step 9:
When dividing 0 by 15, we get 0 with a remainder of 0.
Use 0 as the next digit of our solution. 
Result so far: 20215.8
The remainder is 0 after subtracting 0 from 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

The final result is 20215.8 with a remainder of 0.0.