Let's break this down. We're going to add 1125 and 6840 together.

Step 1: We'll start by adding the digits 5 & 0 in column 1 and get 5.

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

Step 3: We'll start by adding the digits 1 & 8 in column 3 and get 9.

Step 4: We'll start by adding the digits 1 & 6 in column 4 and get 7.

So, 1125 + 6840 = 7965.

