OK, let's do this. We've got 6246 and 1312 and we're adding them all together.

Step 1: We'll start by adding the digits 6 & 2 in column 1 and get 8.

Step 2: We'll start by adding the digits 4 & 1 in column 2 and get 5.

Step 3: We'll start by adding the digits 2 & 3 in column 3 and get 5.

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

So, 6246 + 1312 = 7558.

