Okay, let's tackle this math problem. We're starting with 90246 and subtracting 87242.

Step 1: We'll start by subtracting the digit 2 and the borrow 0 from 6 in column 1 and get 4.
4 is the first digit of our result.

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

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

Step 4: We'll start by subtracting the digit 7 and the borrow 0 from 0 in column 4 and get -7.
We add -7 to 10 and get 3 as the next digit of the result.

Step 5: We'll start by subtracting the digit 8 and the borrow 1 from 9 in column 5 and get 0.
0 is the next digit of our result.

So, 90246 - 87242 = 3004.