Alright, let's solve this problem step by step. We have 9000 and 2902 and we're adding them together.

Step 1: We'll start by adding the digits 0 & 2 in column 1 and get 2.

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

Step 3: We'll start by adding the digits 0 & 9 in column 3 and get 9.

Step 4: We'll start by adding the digits 9 & 2 in column 4 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

So, 9000 + 2902 = 11902.

