We have numbers 1212 and 2223. Let's start adding them together.

Step 1: We'll start by adding the digits 2 & 3 in column 1 and get 5.

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 2 & 2 in column 3 and get 4.

Step 4: We'll start by adding the digits 1 & 2 in column 4 and get 3.

So, 1212 + 2223 = 3435.

