Let's dive into this subtraction. We'll start with 99970 and subtract 81249 from it.

Step 1: We'll start by subtracting the digit 9 and the borrow 0 from 0 in column 1 and get -9.
We add -9 to 10 and get 1 as the first digit of the result.

Step 2: We'll start by subtracting the digit 4 and the borrow 1 from 7 in column 2 and get 2.
2 is the next digit of our result.

Step 3: We'll start by subtracting the digit 2 and the borrow 0 from 9 in column 3 and get 7.
7 is the next digit of our result.

Step 4: We'll start by subtracting the digit 1 and the borrow 0 from 9 in column 4 and get 8.
8 is the next digit of our result.

Step 5: We'll start by subtracting the digit 8 and the borrow 0 from 9 in column 5 and get 1.
1 is the next digit of our result.

So, 99970 - 81249 = 18721.