Let's break this down. We're going to add 2154 and 7931 together.

Step 1: We'll start by adding the digits 4 & 1 in column 1 and get 5.

Step 2: We'll start by adding the digits 5 & 3 in column 2 and get 8.

Step 3: We'll start by adding the digits 1 & 9 in column 3 and get 10.
We'll write down the last digit 0 and carry the 1 to the next column.

Step 4: We'll start by adding the digits 2 & 7 in column 4 and get 10.
We'll write down the last digit 0 and carry the 1 to the next column.

So, 2154 + 7931 = 10085.

