No problem, let's work through this together. We're starting with 999509 and are subtracting 71644 from it.

Step 1: We'll start by subtracting the digit 4 and the borrow 0 from 9 in column 1 and get 5.
5 is the first digit of our result.

Step 2: We'll start by subtracting the digit 4 and the borrow 0 from 0 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 6 and the borrow 1 from 5 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 1 and the borrow 1 from 9 in column 4 and get 7.
7 is the next digit of our result.

Step 5: We'll start by subtracting the digit 7 and the borrow 0 from 9 in column 5 and get 2.
2 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, 999509 - 71644 = 927865.