Okay, let's tackle this math problem. We're starting with 446909 and subtracting 43209.

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 0 and the borrow 0 from 0 in column 2 and get 0.
0 is the next digit of our result.

Step 3: We'll start by subtracting the digit 2 and the borrow 0 from 9 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.

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

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

So, 446909 - 43209 = 403700.