No problem, let's work through this together. We're starting with 15 and 8454 and adding them all up.

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 & 5 in column 2 and get 6.

Step 3: We'll start by adding the digits 0 & 4 in column 3 and get 4.

Step 4: We'll start by adding the digits 0 & 8 in column 4 and get 8.

So, 15 + 8454 = 8469.

