Alright, let's solve this problem step by step. We have 907947 and 88991, and we're subtracting the second number from the first.

Step 1: We'll start by subtracting the digit 1 and the borrow 0 from 7 in column 1 and get 6.
6 is the first digit of our result.

Step 2: We'll start by subtracting the digit 9 and the borrow 0 from 4 in column 2 and get -5.
We add -5 to 10 and get 5 as the next digit of the result.

Step 3: We'll start by subtracting the digit 9 and the borrow 1 from 9 in column 3 and get -1.
We add -1 to 10 and get 9 as the next digit of the result.

Step 4: We'll start by subtracting the digit 8 and the borrow 1 from 7 in column 4 and get -2.
We add -2 to 10 and get 8 as the next digit of the result.

Step 5: We'll start by subtracting the digit 8 and the borrow 1 from 0 in column 5 and get -9.
We add -9 to 10 and get 1 as the next digit of the result.

Step 6: We'll start by subtracting the digit 0 and the borrow 1 from 9 in column 6 and get 8.
8 is the next digit of our result.

So, 907947 - 88991 = 818956.