We have numbers 9906 and 3962. Let's start adding them together.

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

Step 2: We'll start by adding the digits 0 & 6 in column 2 and get 6.

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 & 3 in column 4 and get 13.
We'll write down the last digit 3 and carry the 1 to the next column.

So, 9906 + 3962 = 13868.

