We have numbers 469 and 400. Let's start adding them together.

Step 1: We'll start by adding the digits 9 & 0 in column 1 and get 9.

Step 2: We'll start by adding the digits 6 & 0 in column 2 and get 6.

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

So, 469 + 400 = 869.

