Okay, let's tackle this math problem. We're starting with 84878 and subtracting 71348.

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

Step 2: We'll start by subtracting the digit 4 and the borrow 0 from 7 in column 2 and get 3.
3 is the next digit of our result.

Step 3: We'll start by subtracting the digit 3 and the borrow 0 from 8 in column 3 and get 5.
5 is the next digit of our result.

Step 4: We'll start by subtracting the digit 1 and the borrow 0 from 4 in column 4 and get 3.
3 is the next digit of our result.

Step 5: We'll start by subtracting the digit 7 and the borrow 0 from 8 in column 5 and get 1.
1 is the next digit of our result.

So, 84878 - 71348 = 13530.