We have numbers 2278 and 6321. Let's start adding them together.

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

Step 2: We'll start by adding the digits 7 & 2 in column 2 and get 9.

Step 3: We'll start by adding the digits 2 & 3 in column 3 and get 5.

Step 4: We'll start by adding the digits 2 & 6 in column 4 and get 8.

So, 2278 + 6321 = 8599.

