No problem, let's work through this together. We're starting with 2100 and 9813 and adding them all up.

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 0 & 1 in column 2 and get 1.

Step 3: We'll start by adding the digits 1 & 8 in column 3 and get 9.

Step 4: We'll start by adding the digits 2 & 9 in column 4 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

So, 2100 + 9813 = 11913.

