Here we go! We're going to add 2603 and 4321 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 & 2 in column 2 and get 2.

Step 3: We'll start by adding the digits 6 & 3 in column 3 and get 9.

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

So, 2603 + 4321 = 6924.

