We've got two numbers: 5541 and 8004. Let's find their sum.

Step 1: We'll start by adding the digits 1 & 4 in column 1 and get 5.

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

Step 3: We'll start by adding the digits 5 & 0 in column 3 and get 5.

Step 4: We'll start by adding the digits 5 & 8 in column 4 and get 13.
We'll write down the last digit 3 and carry the 1 to the next column.

So, 5541 + 8004 = 13545.

