Alright, let's solve this problem step by step. We have 2398 and 3861 and we're adding them together.

Step 1: We'll start by adding the digits 8 & 1 in column 1 and get 9.

Step 2: We'll start by adding the digits 9 & 6 in column 2 and get 15.
We'll write down the last digit 5 and carry the 1 to the next column.

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

Step 4: We'll start by adding the digits 2 & 3 in column 4 and get 6.

So, 2398 + 3861 = 6259.

