Alright, let's solve this problem step by step. We have 1312 and 6404 and we're adding them together.

Step 1: We'll start by adding the digits 2 & 4 in column 1 and get 6.

Step 2: We'll start by adding the digits 1 & 0 in column 2 and get 1.

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

Step 4: We'll start by adding the digits 1 & 6 in column 4 and get 7.

So, 1312 + 6404 = 7716.

