Let's break this down. We're going to add 4104 and 2685 together.

Step 1: We'll start by adding the digits 4 & 5 in column 1 and get 9.

Step 2: We'll start by adding the digits 0 & 8 in column 2 and get 8.

Step 3: We'll start by adding the digits 1 & 6 in column 3 and get 7.

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

So, 4104 + 2685 = 6789.

