Alright, let's solve this problem step by step. We have 3450 and 6139 and we're adding them together.

Step 1: We'll start by adding the digits 0 & 9 in column 1 and get 9.

Step 2: We'll start by adding the digits 5 & 3 in column 2 and get 8.

Step 3: We'll start by adding the digits 4 & 1 in column 3 and get 5.

Step 4: We'll start by adding the digits 3 & 6 in column 4 and get 9.

So, 3450 + 6139 = 9589.

