Let's break this down. We're going to add 1 and 7942 together.

Step 1: We'll start by adding the digits 1 & 2 in column 1 and get 3.

Step 2: We'll start by adding the digits 0 & 4 in column 2 and get 4.

Step 3: We'll start by adding the digits 0 & 9 in column 3 and get 9.

Step 4: We'll start by adding the digits 0 & 7 in column 4 and get 7.

So, 1 + 7942 = 7943.

