Okay, we are tasked with adding 550 and 8123. Let's begin!

Step 1: We'll start by adding the digits 0 & 3 in column 1 and get 3.

Step 2: We'll start by adding the digits 5 & 2 in column 2 and get 7.

Step 3: We'll start by adding the digits 5 & 1 in column 3 and get 6.

Step 4: We'll start by adding the digits 0 & 8 in column 4 and get 8.

So, 550 + 8123 = 8673.

