Okay, we are given 5220 and 2403. Let's add them up step by step.

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 2 & 0 in column 2 and get 2.

Step 3: We'll start by adding the digits 2 & 4 in column 3 and get 6.

Step 4: We'll start by adding the digits 5 & 2 in column 4 and get 7.

So, 5220 + 2403 = 7623.

