Let's dive into this subtraction. We'll start with 70458 and subtract 19909 from it.

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

Step 2: We'll start by subtracting the digit 0 and the borrow 1 from 5 in column 2 and get 4.
4 is the next digit of our result.

Step 3: We'll start by subtracting the digit 9 and the borrow 0 from 4 in column 3 and get -5.
We add -5 to 10 and get 5 as the next digit of the result.

Step 4: We'll start by subtracting the digit 9 and the borrow 1 from 0 in column 4 and get -10.
We add -10 to 10 and get 0 as the next digit of the result.

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

So, 70458 - 19909 = 50549.