OK, let's do this. We've got 3603 and 1231 and we're adding them all together.

Step 1: We'll start by adding the digits 3 & 1 in column 1 and get 4.

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 6 & 2 in column 3 and get 8.

Step 4: We'll start by adding the digits 3 & 1 in column 4 and get 4.

So, 3603 + 1231 = 4834.

