Okay, let's tackle this math problem. We're starting with 77015 and subtracting 65091.

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

Step 2: We'll start by subtracting the digit 9 and the borrow 0 from 1 in column 2 and get -8.
We add -8 to 10 and get 2 as the next digit of the result.

Step 3: We'll start by subtracting the digit 0 and the borrow 1 from 0 in column 3 and get -1.
We add -1 to 10 and get 9 as the next digit of the result.

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

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

So, 77015 - 65091 = 11924.