Let's break this down. We're going to add 9963 and 1918 together.

Step 1: We'll start by adding the digits 3 & 8 in column 1 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

Step 2: We'll start by adding the digits 6 & 1 in column 2 and get 8.

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 9 & 1 in column 4 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

So, 9963 + 1918 = 11881.

