Let's break this down. We're going to add 3423 and 4075 together.

Step 1: We'll start by adding the digits 3 & 5 in column 1 and get 8.

Step 2: We'll start by adding the digits 2 & 7 in column 2 and get 9.

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

Step 4: We'll start by adding the digits 3 & 4 in column 4 and get 7.

So, 3423 + 4075 = 7498.

