Okay, let's tackle this math problem. We're starting with 76840 and subtracting 6179.

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

Step 2: We'll start by subtracting the digit 7 and the borrow 1 from 4 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 1 and the borrow 1 from 8 in column 3 and get 6.
6 is the next digit of our result.

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

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

So, 76840 - 6179 = 70661.