Okay, we are given 2400 and 6478. Let's add them up step by step.

Step 1: We'll start by adding the digits 0 & 8 in column 1 and get 8.

Step 2: We'll start by adding the digits 0 & 7 in column 2 and get 7.

Step 3: We'll start by adding the digits 4 & 4 in column 3 and get 8.

Step 4: We'll start by adding the digits 2 & 6 in column 4 and get 8.

So, 2400 + 6478 = 8878.

