Alright, let's solve this problem step by step. We have 2685 and 1121 and we're adding them together.

Step 1: We'll start by adding the digits 5 & 1 in column 1 and get 6.

Step 2: We'll start by adding the digits 8 & 2 in column 2 and get 10.
We'll write down the last digit 0 and carry the 1 to the next column.

Step 3: We'll start by adding the digits 6 & 1 in column 3 and get 8.

Step 4: We'll start by adding the digits 2 & 1 in column 4 and get 3.

So, 2685 + 1121 = 3806.

