Sure thing! We've got 70009 and 48990, and we're going to subtract the second number from the first.

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

Step 2: We'll start by subtracting the digit 9 and the borrow 0 from 0 in column 2 and get -9.
We add -9 to 10 and get 1 as the next digit of the result.

Step 3: We'll start by subtracting the digit 9 and the borrow 1 from 0 in column 3 and get -10.
We add -10 to 10 and get 0 as the next digit of the result.

Step 4: We'll start by subtracting the digit 8 and the borrow 1 from 0 in column 4 and get -9.
We add -9 to 10 and get 1 as the next digit of the result.

Step 5: We'll start by subtracting the digit 4 and the borrow 1 from 7 in column 5 and get 2.
2 is the next digit of our result.

So, 70009 - 48990 = 21019.