Okay, we are given 139 and 3345. Let's add them up step by step.

Step 1: We'll start by adding the digits 9 & 5 in column 1 and get 14.
We'll write down the last digit 4 and carry the 1 to the next column.

Step 2: We'll start by adding the digits 3 & 4 in column 2 and get 8.

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

Step 4: We'll start by adding the digits 0 & 3 in column 4 and get 3.

So, 139 + 3345 = 3484.

