Okay, we are given 1455 and 1002. Let's add them up step by step.

Step 1: We'll start by adding the digits 5 & 2 in column 1 and get 7.

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 & 0 in column 3 and get 4.

Step 4: We'll start by adding the digits 1 & 1 in column 4 and get 2.

So, 1455 + 1002 = 2457.

