We have numbers 6407 and 2401. Let's start adding them 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 & 0 in column 2 and get 0.

Step 3: We'll start by adding the digits 4 & 4 in column 3 and get 8.

Step 4: We'll start by adding the digits 6 & 2 in column 4 and get 8.

So, 6407 + 2401 = 8808.

