Okay, we are given 6442 and 2515. Let's add them up step by step.

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

Step 2: We'll start by adding the digits 4 & 1 in column 2 and get 5.

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

Step 4: We'll start by adding the digits 6 & 2 in column 4 and get 8.

So, 6442 + 2515 = 8957.

