Okay, we are tasked with adding 7480 and 3645. Let's begin!

Step 1: We'll start by adding the digits 0 & 5 in column 1 and get 5.

Step 2: We'll start by adding the digits 8 & 4 in column 2 and get 12.
We'll write down the last digit 2 and carry the 1 to the next column.

Step 3: We'll start by adding the digits 4 & 6 in column 3 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

Step 4: We'll start by adding the digits 7 & 3 in column 4 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

So, 7480 + 3645 = 11125.

