Let's dive into this subtraction. We'll start with 86616 and subtract 12866 from it.

Step 1: We'll start by subtracting the digit 6 and the borrow 0 from 6 in column 1 and get 0.
0 is the first digit of our result.

Step 2: We'll start by subtracting the digit 6 and the borrow 0 from 1 in column 2 and get -5.
We add -5 to 10 and get 5 as the next digit of the result.

Step 3: We'll start by subtracting the digit 8 and the borrow 1 from 6 in column 3 and get -3.
We add -3 to 10 and get 7 as the next digit of the result.

Step 4: We'll start by subtracting the digit 2 and the borrow 1 from 6 in column 4 and get 3.
3 is the next digit of our result.

Step 5: We'll start by subtracting the digit 1 and the borrow 0 from 8 in column 5 and get 7.
7 is the next digit of our result.

So, 86616 - 12866 = 73750.