Okay, we are tasked with adding 6871 and 6617. Let's begin!

Step 1: We'll start by adding the digits 1 & 7 in column 1 and get 8.

Step 2: We'll start by adding the digits 7 & 1 in column 2 and get 8.

Step 3: We'll start by adding the digits 8 & 6 in column 3 and get 14.
We'll write down the last digit 4 and carry the 1 to the next column.

Step 4: We'll start by adding the digits 6 & 6 in column 4 and get 13.
We'll write down the last digit 3 and carry the 1 to the next column.

So, 6871 + 6617 = 13488.

