We've got two numbers: 339 and 502. Let's find their sum.

Step 1: We'll start by adding the digits 9 & 2 in column 1 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

Step 2: We'll start by adding the digits 3 & 0 in column 2 and get 4.

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

So, 339 + 502 = 841.

