Okay, we are given 402 and 434. Let's add them up step by step.

Step 1: We'll start by adding the digits 2 & 4 in column 1 and get 6.

Step 2: We'll start by adding the digits 0 & 3 in column 2 and get 3.

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

So, 402 + 434 = 836.

