Alright, let's solve this problem step by step. We have 659697977 and 520250673, and we're subtracting the second number from the first.

Step 1: We'll start by subtracting the digit 3 and the borrow 0 from 7 in column 1 and get 4.
4 is the first digit of our result.

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

Step 3: We'll start by subtracting the digit 6 and the borrow 0 from 9 in column 3 and get 3.
3 is the next digit of our result.

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

Step 5: We'll start by subtracting the digit 5 and the borrow 0 from 9 in column 5 and get 4.
4 is the next digit of our result.

Step 6: We'll start by subtracting the digit 2 and the borrow 0 from 6 in column 6 and get 4.
4 is the next digit of our result.

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

Step 8: We'll start by subtracting the digit 2 and the borrow 0 from 5 in column 8 and get 3.
3 is the next digit of our result.

Step 9: We'll start by subtracting the digit 5 and the borrow 0 from 6 in column 9 and get 1.
1 is the next digit of our result.

So, 659697977 - 520250673 = 139447304.