Alright, let's solve this problem step by step. We have 9912 and 1002 and we're adding them together.

Step 1: We'll start by adding the digits 2 & 2 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 & 0 in column 3 and get 9.

Step 4: We'll start by adding the digits 9 & 1 in column 4 and get 10.
We'll write down the last digit 0 and carry the 1 to the next column.

So, 9912 + 1002 = 10914.

