Let's break this down. We're going to add 4856 and 4002 together.

Step 1: We'll start by adding the digits 6 & 2 in column 1 and get 8.

Step 2: We'll start by adding the digits 5 & 0 in column 2 and get 5.

Step 3: We'll start by adding the digits 8 & 0 in column 3 and get 8.

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

So, 4856 + 4002 = 8858.

