We have numbers 8811 and 4578. Let's start adding them together.

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

Step 2: We'll start by adding the digits 1 & 7 in column 2 and get 8.

Step 3: We'll start by adding the digits 8 & 5 in column 3 and get 13.
We'll write down the last digit 3 and carry the 1 to the next column.

Step 4: We'll start by adding the digits 8 & 4 in column 4 and get 13.
We'll write down the last digit 3 and carry the 1 to the next column.

So, 8811 + 4578 = 13389.

