Okay, we are given 4323 and 15. Let's add them up step by step.

Step 1: We'll start by adding the digits 3 & 5 in column 1 and get 8.

Step 2: We'll start by adding the digits 2 & 1 in column 2 and get 3.

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

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

So, 4323 + 15 = 4338.

