We are presented with 3450 and 72. Let's work out the sum.

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

Step 2: We'll start by adding the digits 5 & 7 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 & 0 in column 3 and get 5.

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

So, 3450 + 72 = 3522.

