Okay, let's tackle this math problem. We're starting with 336989 and subtracting 78740.

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

Step 2: We'll start by subtracting the digit 4 and the borrow 0 from 8 in column 2 and get 4.
4 is the next digit of our result.

Step 3: We'll start by subtracting the digit 7 and the borrow 0 from 9 in column 3 and get 2.
2 is the next digit of our result.

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

Step 5: We'll start by subtracting the digit 7 and the borrow 1 from 3 in column 5 and get -5.
We add -5 to 10 and get 5 as the next digit of the result.

Step 6: We'll start by subtracting the digit 0 and the borrow 1 from 3 in column 6 and get 2.
2 is the next digit of our result.

So, 336989 - 78740 = 258249.