Let's break this down. We're going to add 4378 and 620 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 7 & 2 in column 2 and get 9.

Step 3: We'll start by adding the digits 3 & 6 in column 3 and get 9.

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

So, 4378 + 620 = 4998.

