We are presented with 618 and 687. Let's work out the sum.

Step 1: We'll start by adding the digits 8 & 7 in column 1 and get 15.
We'll write down the last digit 5 and carry the 1 to the next column.

Step 2: We'll start by adding the digits 1 & 8 in column 2 and get 10.
We'll write down the last digit 0 and carry the 1 to the next column.

Step 3: We'll start by adding the digits 6 & 6 in column 3 and get 13.
We'll write down the last digit 3 and carry the 1 to the next column.

So, 618 + 687 = 1305.

