No problem, let's work through this together. We're starting with 81903 and are subtracting 49968 from it.

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 6 and the borrow 1 from 0 in column 2 and get -7.
We add -7 to 10 and get 3 as the next digit of the result.

Step 3: We'll start by subtracting the digit 9 and the borrow 1 from 9 in column 3 and get -1.
We add -1 to 10 and get 9 as the next digit of the result.

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

Step 5: We'll start by subtracting the digit 4 and the borrow 1 from 8 in column 5 and get 3.
3 is the next digit of our result.

So, 81903 - 49968 = 31935.