Let's solve this addition problem. We have 1213 and 3124, and we need to add them together.

Step 1: We'll start by adding the digits 3 & 4 in column 1 and get 7.

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 & 1 in column 3 and get 3.

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

So, 1213 + 3124 = 4337.

