We have numbers 3003 and 1213. Let's start adding them together.

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 0 & 1 in column 2 and get 1.

Step 3: We'll start by adding the digits 0 & 2 in column 3 and get 2.

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

So, 3003 + 1213 = 4216.

