Let's break this down. We're going to add 3407 and 171 together.

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

Step 2: We'll start by adding the digits 0 & 7 in column 2 and get 7.

Step 3: We'll start by adding the digits 4 & 1 in column 3 and get 5.

Step 4: We'll start by adding the digits 3 & 0 in column 4 and get 3.

So, 3407 + 171 = 3578.

