OK, let's do this. We've got 809400125 and 372490576, and we're subtracting the second number from the first.

Step 1: We'll start by subtracting the digit 6 and the borrow 0 from 5 in column 1 and get -1.
We add -1 to 10 and get 9 as the first digit of the result.

Step 2: We'll start by subtracting the digit 7 and the borrow 1 from 2 in column 2 and get -6.
We add -6 to 10 and get 4 as the next digit of the result.

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

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

Step 5: We'll start by subtracting the digit 9 and the borrow 1 from 0 in column 5 and get -10.
We add -10 to 10 and get 0 as the next digit of the result.

Step 6: We'll start by subtracting the digit 4 and the borrow 1 from 4 in column 6 and get -1.
We add -1 to 10 and get 9 as the next digit of the result.

Step 7: We'll start by subtracting the digit 2 and the borrow 1 from 9 in column 7 and get 6.
6 is the next digit of our result.

Step 8: We'll start by subtracting the digit 7 and the borrow 0 from 0 in column 8 and get -7.
We add -7 to 10 and get 3 as the next digit of the result.

Step 9: We'll start by subtracting the digit 3 and the borrow 1 from 8 in column 9 and get 4.
4 is the next digit of our result.

So, 809400125 - 372490576 = 436909549.