Let's solve this addition problem. We have 5218 and 3021, and we need to add them together.

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

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

Step 3: We'll start by adding the digits 2 & 0 in column 3 and get 2.

Step 4: We'll start by adding the digits 5 & 3 in column 4 and get 8.

So, 5218 + 3021 = 8239.

