Alright, ready to do some subtraction? We're taking 8636 and subtracting 3391 from it.

Step 1: We'll start by subtracting the digit 1 and the borrow 0 from 6 in column 1 and get 5.
5 is the first digit of our result.

Step 2: We'll start by subtracting the digit 9 and the borrow 0 from 3 in column 2 and get -6.
We add -6 to 10 and get 4 as the next digit of the result.

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

Step 4: We'll start by subtracting the digit 3 and the borrow 0 from 8 in column 4 and get 5.
5 is the next digit of our result.

So, 8636 - 3391 = 5245.