Let's dive into this subtraction. We'll start with 902604574 and subtract 260152849 from it.

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 4 and the borrow 1 from 7 in column 2 and get 2.
2 is the next digit of our result.

Step 3: We'll start by subtracting the digit 8 and the borrow 0 from 5 in column 3 and get -3.
We add -3 to 10 and get 7 as the next digit of the result.

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

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

Step 6: We'll start by subtracting the digit 1 and the borrow 1 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 2 in column 7 and get 2.
2 is the next digit of our result.

Step 8: We'll start by subtracting the digit 6 and the borrow 0 from 0 in column 8 and get -6.
We add -6 to 10 and get 4 as the next digit of the result.

Step 9: We'll start by subtracting the digit 2 and the borrow 1 from 9 in column 9 and get 6.
6 is the next digit of our result.

So, 902604574 - 260152849 = 642451725.