OK, let's do this. We've got 66339 and 49539, and we're subtracting the second number from the first.

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

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

Step 3: We'll start by subtracting the digit 5 and the borrow 0 from 3 in column 3 and get -2.
We add -2 to 10 and get 8 as the next digit of the result.

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

Step 5: We'll start by subtracting the digit 4 and the borrow 1 from 6 in column 5 and get 1.
1 is the next digit of our result.

So, 66339 - 49539 = 16800.