We have numbers 7273 and 6645. Let's start adding them together.

Step 1: We'll start by adding the digits 3 & 5 in column 1 and get 8.

Step 2: We'll start by adding the digits 7 & 4 in column 2 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

Step 3: We'll start by adding the digits 2 & 6 in column 3 and get 9.

Step 4: We'll start by adding the digits 7 & 6 in column 4 and get 13.
We'll write down the last digit 3 and carry the 1 to the next column.

So, 7273 + 6645 = 13918.

