Let's dive into this subtraction. We'll start with 989990 and subtract 28291 from it.

Step 1: We'll start by subtracting the digit 1 and the borrow 0 from 0 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 9 and the borrow 1 from 9 in column 2 and get -1.
We add -1 to 10 and get 9 as the next digit of the result.

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

Step 4: We'll start by subtracting the digit 8 and the borrow 0 from 9 in column 4 and get 1.
1 is the next digit of our result.

Step 5: We'll start by subtracting the digit 2 and the borrow 0 from 8 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 9 in column 6 and get 9.
9 is the next digit of our result.

So, 989990 - 28291 = 961699.