Let's dive into this subtraction. We'll start with 46012 and subtract 32878 from it.

Step 1: We'll start by subtracting the digit 8 and the borrow 0 from 2 in column 1 and get -6.
We add -6 to 10 and get 4 as the first digit of the result.

Step 2: We'll start by subtracting the digit 7 and the borrow 1 from 1 in column 2 and get -7.
We add -7 to 10 and get 3 as the next digit of the result.

Step 3: We'll start by subtracting the digit 8 and the borrow 1 from 0 in column 3 and get -9.
We add -9 to 10 and get 1 as the next digit of the result.

Step 4: We'll start by subtracting the digit 2 and the borrow 1 from 6 in column 4 and get 3.
3 is the next digit of our result.

Step 5: We'll start by subtracting the digit 3 and the borrow 0 from 4 in column 5 and get 1.
1 is the next digit of our result.

So, 46012 - 32878 = 13134.