Okay, we are tasked with adding 3004 and 7008. Let's begin!

Step 1: We'll start by adding the digits 4 & 8 in column 1 and get 12.
We'll write down the last digit 2 and carry the 1 to the next column.

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

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

Step 4: We'll start by adding the digits 3 & 7 in column 4 and get 10.
We'll write down the last digit 0 and carry the 1 to the next column.

So, 3004 + 7008 = 10012.

