Let's break this down. We're going to add 5181 and 723 together.

Step 1: We'll start by adding the digits 1 & 3 in column 1 and get 4.

Step 2: We'll start by adding the digits 8 & 2 in column 2 and get 10.
We'll write down the last digit 0 and carry the 1 to the next column.

Step 3: We'll start by adding the digits 1 & 7 in column 3 and get 9.

Step 4: We'll start by adding the digits 5 & 0 in column 4 and get 5.

So, 5181 + 723 = 5904.

