Alright, let's solve this problem step by step. We have 6845 and 3107, and we're subtracting the second number from the first.

Step 1: We'll start by subtracting the digit 7 and the borrow 0 from 5 in column 1 and get -2.
We add -2 to 10 and get 8 as the first digit of the result.

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

Step 3: We'll start by subtracting the digit 1 and the borrow 0 from 8 in column 3 and get 7.
7 is the next digit of our result.

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

So, 6845 - 3107 = 3738.