OK, let's do this. We've got 1700 and 7239 and we're adding them all together.

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

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

Step 3: We'll start by adding the digits 7 & 2 in column 3 and get 9.

Step 4: We'll start by adding the digits 1 & 7 in column 4 and get 8.

So, 1700 + 7239 = 8939.

