Alright, let's solve this problem step by step. We have 1515 and 4074 and we're adding them together.

Step 1: We'll start by adding the digits 5 & 4 in column 1 and get 9.

Step 2: We'll start by adding the digits 1 & 7 in column 2 and get 8.

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 1 & 4 in column 4 and get 5.

So, 1515 + 4074 = 5589.

