We've got two numbers: 7455 and 800. Let's find their sum.

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

Step 2: We'll start by adding the digits 5 & 0 in column 2 and get 5.

Step 3: We'll start by adding the digits 4 & 8 in column 3 and get 12.
We'll write down the last digit 2 and carry the 1 to the next column.

Step 4: We'll start by adding the digits 7 & 0 in column 4 and get 8.

So, 7455 + 800 = 8255.

