Alright, let's solve this problem step by step. We have 862 and 398 and we're adding them together.

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

Step 2: We'll start by adding the digits 6 & 9 in column 2 and get 16.
We'll write down the last digit 6 and carry the 1 to the next column.

Step 3: We'll start by adding the digits 8 & 3 in column 3 and get 12.
We'll write down the last digit 2 and carry the 1 to the next column.

So, 862 + 398 = 1260.

