Not to worry, we've got 5823 and 4155. Let's get to adding them!

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 & 5 in column 2 and get 7.

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, 5823 + 4155 = 9978.

