Let's break this down. We're going to add 5454 and 7040 together.

Step 1: We'll start by adding the digits 4 & 0 in column 1 and get 4.

Step 2: We'll start by adding the digits 5 & 4 in column 2 and get 9.

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

Step 4: We'll start by adding the digits 5 & 7 in column 4 and get 12.
We'll write down the last digit 2 and carry the 1 to the next column.

So, 5454 + 7040 = 12494.

