Alright, let's solve this problem step by step. We have 126 and 703 and we're adding them together.

Step 1: We'll start by adding the digits 6 & 3 in column 1 and get 9.

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

Step 3: We'll start by adding the digits 1 & 7 in column 3 and get 8.

So, 126 + 703 = 829.

