Not to worry, we've got 1205 and 3104. Let's get to adding them!

Step 1: We'll start by adding the digits 5 & 4 in column 1 and get 9.

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

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, 1205 + 3104 = 4309.

