No problem, let's work through this together. We're starting with 666827 and are subtracting 3958 from it.

Step 1: We'll start by subtracting the digit 8 and the borrow 0 from 7 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 5 and the borrow 1 from 2 in column 2 and get -4.
We add -4 to 10 and get 6 as the next digit of the result.

Step 3: We'll start by subtracting the digit 9 and the borrow 1 from 8 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 3 and the borrow 1 from 6 in column 4 and get 2.
2 is the next digit of our result.

Step 5: We'll start by subtracting the digit 0 and the borrow 0 from 6 in column 5 and get 6.
6 is the next digit of our result.

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

So, 666827 - 3958 = 662869.