OK, let's do this. We've got 7144 and 1231 and we're adding them all together.

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

Step 2: We'll start by adding the digits 4 & 3 in column 2 and get 7.

Step 3: We'll start by adding the digits 1 & 2 in column 3 and get 3.

Step 4: We'll start by adding the digits 7 & 1 in column 4 and get 8.

So, 7144 + 1231 = 8375.

