Okay, let's tackle this math problem. We're starting with 55518 and subtracting 53115.

Step 1: We'll start by subtracting the digit 5 and the borrow 0 from 8 in column 1 and get 3.
3 is the first digit of our result.

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

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

Step 4: We'll start by subtracting the digit 3 and the borrow 0 from 5 in column 4 and get 2.
2 is the next digit of our result.

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

So, 55518 - 53115 = 2403.