Alright, let's solve this problem step by step. We have 257 and 2520 and we're adding them together.

Step 1: We'll start by adding the digits 7 & 0 in column 1 and get 7.

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

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

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

So, 257 + 2520 = 2777.

