No problem, let's work through this together. We're starting with 5821 and 4172 and adding them all up.

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

Step 2: We'll start by adding the digits 2 & 7 in column 2 and get 9.

Step 3: We'll start by adding the digits 8 & 1 in column 3 and get 9.

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

So, 5821 + 4172 = 9993.

