Here we go! We're going to add 2439 and 4000 together.

Step 1: We'll start by adding the digits 9 & 0 in column 1 and get 9.

Step 2: We'll start by adding the digits 3 & 0 in column 2 and get 3.

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

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

So, 2439 + 4000 = 6439.

