Let's solve this addition problem. We have 521 and 4057, and we need to add them together.

Step 1: We'll start by adding the digits 1 & 7 in column 1 and get 8.

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

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

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

So, 521 + 4057 = 4578.

