We are presented with 3500 and 4057. Let's work out the sum.

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

Step 2: We'll start by adding the digits 0 & 5 in column 2 and get 5.

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 3 & 4 in column 4 and get 7.

So, 3500 + 4057 = 7557.

