Okay, we are tasked with adding 6403 and 3174. Let's begin!

Step 1: We'll start by adding the digits 3 & 4 in column 1 and get 7.

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 6 & 3 in column 4 and get 9.

So, 6403 + 3174 = 9577.

