Got it! So, we have 21018 and 8238, and we'll subtract the latter from the former.

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

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

Step 3: We'll start by subtracting the digit 2 and the borrow 1 from 0 in column 3 and get -3.
We add -3 to 10 and get 7 as the next digit of the result.

Step 4: We'll start by subtracting the digit 8 and the borrow 1 from 1 in column 4 and get -8.
We add -8 to 10 and get 2 as the next digit of the result.

Step 5: We'll start by subtracting the digit 0 and the borrow 1 from 2 in column 5 and get 1.
1 is the next digit of our result.

So, 21018 - 8238 = 12780.