Alright, let's solve this problem step by step. We have 6404 and 9434 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 & 3 in column 2 and get 3.

Step 3: We'll start by adding the digits 4 & 4 in column 3 and get 8.

Step 4: We'll start by adding the digits 6 & 9 in column 4 and get 15.
We'll write down the last digit 5 and carry the 1 to the next column.

So, 6404 + 9434 = 15838.

