Okay, let's tackle this math problem. We're starting with 698994 and subtracting 27079.

Step 1: We'll start by subtracting the digit 9 and the borrow 0 from 4 in column 1 and get -5.
We add -5 to 10 and get 5 as the first digit of the result.

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

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

Step 4: We'll start by subtracting the digit 7 and the borrow 0 from 8 in column 4 and get 1.
1 is the next digit of our result.

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

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

So, 698994 - 27079 = 671915.