We've got two numbers: 9920 and 3213. Let's find their sum.

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

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

Step 3: We'll start by adding the digits 9 & 2 in column 3 and get 11.
We'll write down the last digit 1 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, 9920 + 3213 = 13133.

