Let's break this down. We're going to add 4388 and 4090 together.

Step 1: We'll start by adding the digits 8 & 0 in column 1 and get 8.

Step 2: We'll start by adding the digits 8 & 9 in column 2 and get 17.
We'll write down the last digit 7 and carry the 1 to the next column.

Step 3: We'll start by adding the digits 3 & 0 in column 3 and get 4.

Step 4: We'll start by adding the digits 4 & 4 in column 4 and get 8.

So, 4388 + 4090 = 8478.

