Okay, we are tasked with adding 5373 and 123. Let's begin!

Step 1: We'll start by adding the digits 3 & 3 in column 1 and get 6.

Step 2: We'll start by adding the digits 7 & 2 in column 2 and get 9.

Step 3: We'll start by adding the digits 3 & 1 in column 3 and get 4.

Step 4: We'll start by adding the digits 5 & 0 in column 4 and get 5.

So, 5373 + 123 = 5496.

