Let's break this down. We're going to add 7778 and 4340 together.

Step 1: We'll start by adding the digits 8 & 0 in column 1 and get 8.

Step 2: We'll start by adding the digits 7 & 4 in column 2 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

Step 3: We'll start by adding the digits 7 & 3 in column 3 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

Step 4: We'll start by adding the digits 7 & 4 in column 4 and get 12.
We'll write down the last digit 2 and carry the 1 to the next column.

So, 7778 + 4340 = 12118.

