Okay, we are tasked with adding 5721 and 4038. Let's begin!

Step 1: We'll start by adding the digits 1 & 8 in column 1 and get 9.

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

Step 3: We'll start by adding the digits 7 & 0 in column 3 and get 7.

Step 4: We'll start by adding the digits 5 & 4 in column 4 and get 9.

So, 5721 + 4038 = 9759.

