OK, let's do this. We've got 6521 and 2252 and we're adding them all together.

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 & 5 in column 2 and get 7.

Step 3: We'll start by adding the digits 5 & 2 in column 3 and get 7.

Step 4: We'll start by adding the digits 6 & 2 in column 4 and get 8.

So, 6521 + 2252 = 8773.

