No problem, let's work through this together. We're starting with 816 and 1123 and adding them all up.

Step 1: We'll start by adding the digits 6 & 3 in column 1 and get 9.

Step 2: We'll start by adding the digits 1 & 2 in column 2 and get 3.

Step 3: We'll start by adding the digits 8 & 1 in column 3 and get 9.

Step 4: We'll start by adding the digits 0 & 1 in column 4 and get 1.

So, 816 + 1123 = 1939.

