Okay, we are given 1235 and 3039. Let's add them up step by step.

Step 1: We'll start by adding the digits 5 & 9 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 & 3 in column 2 and get 7.

Step 3: We'll start by adding the digits 2 & 0 in column 3 and get 2.

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

So, 1235 + 3039 = 4274.

