Let's dive into this subtraction. We'll start with 85996 and subtract 84012 from it.

Step 1: We'll start by subtracting the digit 2 and the borrow 0 from 6 in column 1 and get 4.
4 is the first digit of our result.

Step 2: We'll start by subtracting the digit 1 and the borrow 0 from 9 in column 2 and get 8.
8 is the next digit of our result.

Step 3: We'll start by subtracting the digit 0 and the borrow 0 from 9 in column 3 and get 9.
9 is the next digit of our result.

Step 4: We'll start by subtracting the digit 4 and the borrow 0 from 5 in column 4 and get 1.
1 is the next digit of our result.

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

So, 85996 - 84012 = 1984.