We've got two numbers: 668 and 610. Let's find their sum.

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 6 & 1 in column 2 and get 7.

Step 3: We'll start by adding the digits 6 & 6 in column 3 and get 12.
We'll write down the last digit 2 and carry the 1 to the next column.

So, 668 + 610 = 1278.

