Let's break this down. We're going to add 4070 and 4873 together.

Step 1: We'll start by adding the digits 0 & 3 in column 1 and get 3.

Step 2: We'll start by adding the digits 7 & 7 in column 2 and get 14.
We'll write down the last digit 4 and carry the 1 to the next column.

Step 3: We'll start by adding the digits 0 & 8 in column 3 and get 9.

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

So, 4070 + 4873 = 8943.

