No problem, let's work through this together. We're starting with 2402 and 390 and adding them all up.

Step 1: We'll start by adding the digits 2 & 0 in column 1 and get 2.

Step 2: We'll start by adding the digits 0 & 9 in column 2 and get 9.

Step 3: We'll start by adding the digits 4 & 3 in column 3 and get 7.

Step 4: We'll start by adding the digits 2 & 0 in column 4 and get 2.

So, 2402 + 390 = 2792.

