No problem, let's work through this together. We're starting with 8154 and 1235 and adding them all up.

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

Step 2: We'll start by adding the digits 5 & 3 in column 2 and get 8.

Step 3: We'll start by adding the digits 1 & 2 in column 3 and get 3.

Step 4: We'll start by adding the digits 8 & 1 in column 4 and get 9.

So, 8154 + 1235 = 9389.

