Okay, let's tackle this math problem. We're starting with 70643 and subtracting 25154.

Step 1: We'll start by subtracting the digit 4 and the borrow 0 from 3 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 5 and the borrow 1 from 4 in column 2 and get -2.
We add -2 to 10 and get 8 as the next digit of the result.

Step 3: We'll start by subtracting the digit 1 and the borrow 1 from 6 in column 3 and get 4.
4 is the next digit of our result.

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

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

So, 70643 - 25154 = 45489.