Okay, let's tackle this math problem. We're starting with 89981 and subtracting 66913.

Step 1: We'll start by subtracting the digit 3 and the borrow 0 from 1 in column 1 and get -2.
We add -2 to 10 and get 8 as the first digit of the result.

Step 2: We'll start by subtracting the digit 1 and the borrow 1 from 8 in column 2 and get 6.
6 is the next digit of our result.

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

Step 4: We'll start by subtracting the digit 6 and the borrow 0 from 9 in column 4 and get 3.
3 is the next digit of our result.

Step 5: We'll start by subtracting the digit 6 and the borrow 0 from 8 in column 5 and get 2.
2 is the next digit of our result.

So, 89981 - 66913 = 23068.