Okay, we are tasked with adding 4073 and 391. Let's begin!

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

Step 2: We'll start by adding the digits 7 & 9 in column 2 and get 16.
We'll write down the last digit 6 and carry the 1 to the next column.

Step 3: We'll start by adding the digits 0 & 3 in column 3 and get 4.

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

So, 4073 + 391 = 4464.

