Okay, let's tackle this math problem. We're starting with 400443 and subtracting 88138.

Step 1: We'll start by subtracting the digit 8 and the borrow 0 from 3 in column 1 and get -5.
We add -5 to 10 and get 5 as the first digit of the result.

Step 2: We'll start by subtracting the digit 3 and the borrow 1 from 4 in column 2 and get 0.
0 is the next digit of our result.

Step 3: We'll start by subtracting the digit 1 and the borrow 0 from 4 in column 3 and get 3.
3 is the next digit of our result.

Step 4: We'll start by subtracting the digit 8 and the borrow 0 from 0 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 8 and the borrow 1 from 0 in column 5 and get -9.
We add -9 to 10 and get 1 as the next digit of the result.

Step 6: We'll start by subtracting the digit 0 and the borrow 1 from 4 in column 6 and get 3.
3 is the next digit of our result.

So, 400443 - 88138 = 312305.