OK, let's do this. We've got 940299 and 19872, and we're subtracting the second number from the first.

Step 1: We'll start by subtracting the digit 2 and the borrow 0 from 9 in column 1 and get 7.
7 is the first digit of our result.

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

Step 3: We'll start by subtracting the digit 8 and the borrow 0 from 2 in column 3 and get -6.
We add -6 to 10 and get 4 as the next digit of the result.

Step 4: We'll start by subtracting the digit 9 and the borrow 1 from 0 in column 4 and get -10.
We add -10 to 10 and get 0 as the next digit of the result.

Step 5: We'll start by subtracting the digit 1 and the borrow 1 from 4 in column 5 and get 2.
2 is the next digit of our result.

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

So, 940299 - 19872 = 920427.