Got it! So, we have 215399 and 40243, and we'll subtract the latter from the former.

Step 1: We'll start by subtracting the digit 3 and the borrow 0 from 9 in column 1 and get 6.
6 is the first digit of our result.

Step 2: We'll start by subtracting the digit 4 and the borrow 0 from 9 in column 2 and get 5.
5 is the next digit of our result.

Step 3: We'll start by subtracting the digit 2 and the borrow 0 from 3 in column 3 and get 1.
1 is the next digit of our result.

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

Step 5: We'll start by subtracting the digit 4 and the borrow 0 from 1 in column 5 and get -3.
We add -3 to 10 and get 7 as the next digit of the result.

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

So, 215399 - 40243 = 175156.