Let's solve this addition problem. We have 1021 and 5628, and we need to add them together.

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

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

Step 3: We'll start by adding the digits 0 & 6 in column 3 and get 6.

Step 4: We'll start by adding the digits 1 & 5 in column 4 and get 6.

So, 1021 + 5628 = 6649.

