No problem, let's work through this together. We're starting with 871787 and are subtracting 30575 from it.

Step 1: We'll start by subtracting the digit 5 and the borrow 0 from 7 in column 1 and get 2.
2 is the first digit of our result.

Step 2: We'll start by subtracting the digit 7 and the borrow 0 from 8 in column 2 and get 1.
1 is the next digit of our result.

Step 3: We'll start by subtracting the digit 5 and the borrow 0 from 7 in column 3 and get 2.
2 is the next digit of our result.

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

Step 5: We'll start by subtracting the digit 3 and the borrow 0 from 7 in column 5 and get 4.
4 is the next digit of our result.

Step 6: We'll start by subtracting the digit 0 and the borrow 0 from 8 in column 6 and get 8.
8 is the next digit of our result.

So, 871787 - 30575 = 841212.