Alright, let's solve this problem step by step. We have 5257 and 8620 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 & 6 in column 3 and get 8.

Step 4: We'll start by adding the digits 5 & 8 in column 4 and get 13.
We'll write down the last digit 3 and carry the 1 to the next column.

So, 5257 + 8620 = 13877.

