Okay, let's tackle this math problem. We're starting with 96660 and subtracting 642.

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

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

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

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

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

So, 96660 - 642 = 96018.