Let's break this down. We're going to add 1868 and 9819 together.

Step 1: We'll start by adding the digits 8 & 9 in column 1 and get 17.
We'll write down the last digit 7 and carry the 1 to the next column.

Step 2: We'll start by adding the digits 6 & 1 in column 2 and get 8.

Step 3: We'll start by adding the digits 8 & 8 in column 3 and get 16.
We'll write down the last digit 6 and carry the 1 to the next column.

Step 4: We'll start by adding the digits 1 & 9 in column 4 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

So, 1868 + 9819 = 11687.

