Okay, we are tasked with adding 5401 and 3619. Let's begin!

Step 1: We'll start by adding the digits 1 & 9 in column 1 and get 10.
We'll write down the last digit 0 and carry the 1 to the next column.

Step 2: We'll start by adding the digits 0 & 1 in column 2 and get 2.

Step 3: We'll start by adding the digits 4 & 6 in column 3 and get 10.
We'll write down the last digit 0 and carry the 1 to the next column.

Step 4: We'll start by adding the digits 5 & 3 in column 4 and get 9.

So, 5401 + 3619 = 9020.

