Alright, let's solve this problem step by step. We have 2404 and 394 and we're adding them together.

Step 1: We'll start by adding the digits 4 & 4 in column 1 and get 8.

Step 2: We'll start by adding the digits 0 & 9 in column 2 and get 9.

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

Step 4: We'll start by adding the digits 2 & 0 in column 4 and get 2.

So, 2404 + 394 = 2798.

