Let's break this down. We're going to add 42 and 451 together.

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

Step 2: We'll start by adding the digits 4 & 5 in column 2 and get 9.

Step 3: We'll start by adding the digits 0 & 4 in column 3 and get 4.

So, 42 + 451 = 493.

