Here we go! We're going to add 6555 and 1320 together.

Step 1: We'll start by adding the digits 5 & 0 in column 1 and get 5.

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

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

Step 4: We'll start by adding the digits 6 & 1 in column 4 and get 7.

So, 6555 + 1320 = 7875.

