Alright, let's solve this problem step by step. We have 2910 and 9904 and we're adding them together.

Step 1: We'll start by adding the digits 0 & 4 in column 1 and get 4.

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

Step 3: We'll start by adding the digits 9 & 9 in column 3 and get 18.
We'll write down the last digit 8 and carry the 1 to the next column.

Step 4: We'll start by adding the digits 2 & 9 in column 4 and get 12.
We'll write down the last digit 2 and carry the 1 to the next column.

So, 2910 + 9904 = 12814.

