Okay, we are given 6404 and 101. Let's add them up step by step.

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

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

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 & 0 in column 4 and get 6.

So, 6404 + 101 = 6505.

