Let's solve this addition problem. We have 9811 and 9110, and we need to add them together.

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

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

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

Step 4: We'll start by adding the digits 9 & 9 in column 4 and get 18.
We'll write down the last digit 8 and carry the 1 to the next column.

So, 9811 + 9110 = 18921.

