Okay, we are given 6684 and 9605. Let's add them up step by step.

Step 1: We'll start by adding the digits 4 & 5 in column 1 and get 9.

Step 2: We'll start by adding the digits 8 & 0 in column 2 and get 8.

Step 3: We'll start by adding the digits 6 & 6 in column 3 and get 12.
We'll write down the last digit 2 and carry the 1 to the next column.

Step 4: We'll start by adding the digits 6 & 9 in column 4 and get 16.
We'll write down the last digit 6 and carry the 1 to the next column.

So, 6684 + 9605 = 16289.

